Processing device

ABSTRACT

An image processing device includes a correction processor configured to correct print image data by correcting an edge-portion correction area in an edge portion of a print image based on the print image data, the area extending along image edge expressed with a ground color and an upper layer color over the grand color in the edge portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority based on 35 USC 119 from prior JapanesePatent Application No. 2014-106380 filed on May 22, 2014 entitled“PROCESSING DEVICE”, the entire contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure relates to an image processing device, and is suitablefor application to color electrophotographic printers (hereinafter alsoreferred to as color printers), for example.

2. Description of Related Art

A conventional color printer is provided with five image drum unitsarranged in a row. Four of these image drum units form toner images withtoners of four different colors, i.e., cyan, magenta, yellow, and black,which are base colors for the formation of a print image, and theremaining one image drum unit forms a toner image of the same pattern asthat of a base color portion of a print image with toner of one color,such as clear or white, which is a special color for the formation of aprint image. Then, the color printer forms a print image in which thespecial color is laid over the base colors in such a way that the tonerimages of the base colors formed by the four image drum units and thetoner image of the special color formed by the one image drum unit aretransferred sequentially one over another in that order and fixed to asurface of a medium to be printed (print medium). Alternatively, thecolor printer forms a print image in which the base colors are laid overthe special color in such a way that the toner images of the base colorsformed by the four image drum units are transferred sequentially oneover another and fixed to a surface of a print medium, and then thetoner image of the special color formed by the one image drum unit istransferred and fixed thereto (see Patent Literature 1, for example).

[Patent Literature 1] Japanese Patent Application Publication No.2010-152209 (pp. 7, 8, and 14, and FIG. 1)

SUMMARY OF THE INVENTION

A conventional color printer forms a print image in which the specialcolor is laid over the base colors or a print image in which the basecolors are laid over the special color by laying toner images of fivecolors, one over another, on a surface of a print medium. However, insome color printers, the toner images are transferred onto the surfaceof the print medium while being misaligned relative to their idealtransfer positions depending on factors such as the assembly precisionof the printer. In this case, the color printer has a problem that thespecial color spreads out from under the base colors and stands out, orthe base colors spread out from under the special color and stand out inan edge portion of the print image formed on the surface of the printedmedium, which deteriorates the quality of the print image.

An objective of an embodiment of the invention is to provide an imageprocessing device capable of reducing deterioration in the quality of aprint image.

An aspect of the invention is an image processing device that includes acorrection processor configured to correct print image data bycorrecting an edge-portion correction area in an edge portion of a printimage based on the print image data, the area extending along image edgeexpressed with a ground color and an upper color laid over the groundcolor in the edge portion. According to the above aspect of theinvention, in the image edge portion of the print image based on theprint image data, it is possible to make the width of the ground colornarrower than the width of the upper color such that the area of theground color retreats toward the center of the image from the imageedges, or to lower the density of the ground color. By doing so, even ifthe ground color and the upper color are misaligned with each other inthe edge portion of the print image when the image is formed on thesurface of the print medium, it is possible to prevent the ground colorfrom spreading out from under the upper color or make the ground colorspreading out from under the upper color less likely to stand out.Thereby, the deterioration in the quality of the print image can bereduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view illustrating the internal configurationof a color printer according to the invention.

FIG. 2 is a block diagram illustrating the circuit configuration of thecolor printer according to embodiment 1.

FIG. 3 is a block diagram of functional circuit blocks for explainingfirst image processing executed by a first controller.

FIG. 4 is a schematic diagram for explaining the detection of a boundarycorrection area of a print image.

FIG. 5 is a schematic diagram for explaining a first area detectionrange with respect to a print image.

FIG. 6 is a schematic diagram for explaining the detection of anedge-portion correction area for a bordered mode of a print image.

FIG. 7 is a schematic diagram for explaining a first correctionprocessing performed on a print image.

FIG. 8 is a schematic diagram for explaining the formation of a printimage on a surface of a print medium based on corrected print imagedata.

FIGS. 9A to 9C are schematic sectional views for explaining themisregistration of a ground color and an upper color in the case offorming a print image in a conventional color printer.

FIGS. 10A to 10C are schematic sectional views for explaining themisregistration of a ground color and an upper color in the case offorming a print image in the color printer according to embodiment 1.

FIG. 11 is a flowchart illustrating a boundary correction area detectionprocessing procedure.

FIG. 12 is a flowchart illustrating a first edge-portion correction areadetection processing procedure.

FIG. 13 is a flowchart illustrating a first correction processingprocedure.

FIG. 14 is a block diagram illustrating the circuit configuration of acolor printer according to embodiment 2.

FIG. 15 is a block diagram of functional circuit blocks for explaining asecond image processing executed by a second controller.

FIG. 16 is a schematic diagram for explaining the detection of anedge-portion correction area for a borderless mode of a print image.

FIGS. 17A to 17C are schematic sectional views for explaining themisregistration of a ground color and an upper color in the case offorming a print image in a conventional color printer.

FIGS. 18A to 18C are schematic sectional views for explaining themisregistration of a ground color and an upper color in the case offorming a print image in the color printer according to embodiment 2.

FIG. 19 is a flowchart illustrating a second edge-portion correctionarea detection processing procedure.

FIG. 20 is a flowchart illustrating a second correction processingprocedure.

DETAILED DESCRIPTION OF EMBODIMENTS

Descriptions are provided hereinbelow for embodiments based on thedrawings. In the respective drawings referenced herein, the sameconstituents are designated by the same reference numerals and duplicateexplanation concerning the same constituents is omitted. All of thedrawings are provided to illustrate the respective examples only.

Note that the description is provided in the following order: (1)Embodiment 1, (2) Embodiment 2, and (3) Other Embodiments.

(1) Embodiment 1 (1-1) Internal Configuration of a Color Printer

In FIG. 1, throughout the description, reference numeral 1 denotes colorprinter 1 of a secondary transfer type according to the invention. Colorprinter 1 includes, for example, printer chassis 2 of substantially abox shape whose front surface 2A is a right edge surface in the drawing.Incidentally, in the following description, an upward direction denotedby arrow al in the drawing when color printer 1 is viewed while facingfront surface 2A is also referred to as a printer upward direction and adirection opposite the upward direction is also referred to as a printerdownward direction. These directions are also referred to as a printerupward/downward direction collectively when these need not beparticularly distinguished from each other or both of these are meant.In addition, in the following description, a forward direction denotedby arrow b1 in the drawing when color printer 1 is viewed while facingfront surface 2A is also referred to as a printer forward direction anda direction opposite the forward direction is also referred to as aprinter backward direction. These directions are also referred to as aprinter forward/backward direction collectively when these need not beparticularly distinguished from each other or both of these are meant.Further, in the following description, a leftward direction denoted byarrow c1 in the drawing when color printer 1 is viewed while facingfront surface 2A is also referred to as a printer leftward direction anda direction opposite the leftward direction is also referred to as arightward direction. These directions are also referred to as a printerleftward/rightward direction collectively when these need not beparticularly distinguished from each other or both of these are meant.Furthermore, in the following description, a rotation direction denotedby arrow dl in the drawing, which is about an axis parallel with theprinter leftward/rightward direction, is also referred to as onerotation direction and a direction opposite this direction is alsoreferred to as the other rotation direction.

Manipulation panel 4 having various manipulation keys, a touch screen,and the like is disposed in, for example, a front edge portion of uppersurface 2B of printer chassis 2. Moreover, in upper surface 2B, printerchassis 2 is provided with medium delivery section 2BX that placesthereon a rectangular medium to be printed (print medium 5), forexample, having a print image formed thereon and delivers it to theuser. Medium ejection port 2BY is formed in a rear inner wall of thismedium delivery section 2BX. On the other hand, image formation section7 for forming a print image on a surface of print medium 5 is disposedin a central portion of printer chassis 2. Image formation section 7includes five, namely, a first to fifth, image formation units 10 to 14,transfer unit 15, and fixation unit 16, for example.

First to fifth image formation units 10 to 14 are detachably attached tobe arranged in a row in the printer rearward direction. In this respect,four rear image formation units, namely, second to fifth image formationunits 11 to 14, each hold toner as a developer of any of the fourcolors, i.e., black (K), yellow (Y), magenta (M), and cyan (C), forexample, which are base colors for the formation of a print image, suchthat image formation units 11 to 14 hold the colors different from eachother. Meanwhile, one foremost image formation unit, namely, first imageformation unit 10 holds toner of white (W), for example, which is aspecial color for the formation of a print image. First to fifth imageformation units 10 to 14 are configured to respectively formelectrostatic latent images on the surfaces of first to fifthphotoconductive drums 20 to 24, which are image carriers that rotate inthe one rotation direction, by irradiating respectively the surfaces ofthe photoconductive drums with exposure light using first to fifth LED(light emitting diode) heads 25 to 29, which are exposure units that arecontrolled based on corresponding color components of a print image, andthen form toner images, which are developer images, by developing theelectrostatic latent images with toner. Note that, first image formationunit 10 may be replaced with a unit holding a toner of clear (CL) whichis a special color, for example, since this unit is attachable to anddetachable from printer chassis 2.

In transfer unit 15, endless transfer belt 33 is stretched around beltdrive roller 30, driven roller 31, and backup roller 32 that rotate inthe other rotation direction. Transfer unit 15 is configured totransfer, sequentially one over another, the toner images of first tofifth photoconductive drums 20 to 24 onto the surface of transfer belt33 between belt drive roller 30 and driven roller 31 with five primarytransfer rollers 34 to 38, and transfer the toner images on transferbelt 33 onto the surface of print medium 5 with secondary transferroller 39 facing backup roller 32. Note that transfer unit 15 hascleaning blade 40 provided in its rear end portion such that one endportion of cleaning blade 40 is pressed against the surface of transferbelt 33. Thereby, transfer unit 15 can remove toner, which remainsun-transferred on the surface of print medium 5, from the surface oftransfer belt 33 by use of cleaning blade 40. The fixation unit isconfigured to apply heat and pressure on the toner image transferred onthe surface of print medium 5 by transfer unit 15, and thus melt and fixthe toner image to the surface of print medium 5 to form a print imagethereon.

In addition, medium supply section 43 is disposed inside printer chassis2 in its lower end portion. Medium supply section 43 is configured tofeed one print medium 5 at a time with feed roller 42 from mediacassette 41 that is loaded with print media 5. Note that color printer 1can use various print media 5, such as white plain paper and plain paperof colors other than white of a predefined medium size, and transferpaper for printing on a T-shirt, for formation of a print image byloading these various print media 5 in media cassette 41. Moreover, atransport section for medium supply 44 is provided inside printerchassis 2 in its front lower end portion. Transport section for mediumsupply 44 is configured to transport print medium 5 fed from mediacassette 41 to image formation section 7 through a transport path forthe medium supply. Further, a transport section for medium ejection 45is provided inside printer chassis 2 in its rear end portion. Thetransport section for medium ejection 45 is configured to transportprint medium 5 fed from fixation unit 16 to medium ejection port 2BYthrough a transport path for the medium ejection. Furthermore, atransport section for medium resupply 46 is provided inside printerchassis 2 between image formation section 7 and medium supply section43. The transport section for medium resupply 46 is configured totransport print medium 5 fed from fixation unit 16 back to the transportsection for medium supply 44 through a transport path for the mediumresupply. Besides, separator 47 is disposed inside printer chassis 2.Separator 47 is configured to change the path to transport print medium5 fed from fixation unit 16 between the transport path for mediumejection and the transport path for medium resupply.

In the situation where first image formation unit 10 holding white toneris attached to color printer 1 and plain paper of white or another coloris loaded in media cassette 41 as print medium 5, for example, theprinter forms toner images of black, yellow, magenta, and cyan on thesurfaces of second to fifth photoconductive drums 21 to 24 with secondto fifth image formation units 11 to 14 and forms a white toner image,having substantially the same pattern as that of a black, yellow,magenta, and cyan portion of a print image, on the surface of firstphotoconductive drum 20 with first image formation unit 10, thentransfers the toner images onto the surface of transfer belt 33 one overanother in the order of cyan, magenta, yellow, black, and white, andthen transfers the toner images of five colors, thus formed on transferbelt 33, onto a surface of a plain paper sheet that is transported frommedium supply section 43 through the transport path for medium supply.Further, after color printer 1 forms a print image represented with thebase colors and the special color by fixing the toner images of fivecolors to the surface of the plain paper sheet with fixation unit 16, ittransports the plain paper sheet to medium ejection port 2BY through thetransport path for medium ejection and ejects it to medium deliverysection 2BX. Here, color printer 1 transfers the toner images of fivecolors, thus transferred on the surface of transfer belt 33, upside downonto the surface of the plain paper sheet. As a result, the white tonerimage is interposed between the surface of the plain paper sheet and thetoner images of the base colors, and white serves as a foundation forthe base colors in the print image. Thereby, thanks to white serving asthe foundation for the base colors, color printer 1 can represent theprint image with the base colors as clear as their original colors nomatter which of a white plain paper sheet and a plain paper sheet ofanother color is used as print medium 5 on which the print image isformed.

On the other hand, in the situation where first image formation unit 10holding white toner is attached to color printer 1 and transfer paper isloaded in media cassette 41 as print medium 5, the printer forms tonerimages on the surfaces of second to fifth photoconductive drums 21 to 24with second to fifth image formation units 11 to 14. and transfers thetoner images onto the surface of transfer belt 33 one over another inthe order of cyan, magenta, yellow, and black, and then transfers thetoner images of four colors, thus formed on transfer belt 33, onto asurface of a transfer paper sheet that is transported from medium supplysection 43 through the transport path for medium supply. Note that, inthis event, color printer 1 changes a medium transport path withseparator 47 to supply the transfer paper sheet, which is fed fromfixation unit 16 with a print image represented only with the basecolors formed thereon, to image formation section 7 again by way of thetransport path for medium resupply and the transport path for mediumsupply, in this order. While the sheet is being resupplied, colorprinter 1 forms a white toner image, having substantially the samepattern as that of a black, yellow, magenta, and cyan portion of a printimage, on the surface of first photoconductive drum 20 with first imageformation unit 10 and transfers the toner image onto the surface oftransfer belt 33. Then, the printer transfers the toner image, thusformed on transfer belt 33, onto the surface of the resupplied transferpaper sheet such that the toner image is laid over the print image onthe surface of the sheet. After color printer 1 forms a print imagerepresented with the special color as well as the base color by fixingthe white toner image to the print image on the surface of the transferpaper sheet with fixation unit 16, the printer changes the mediumtransport path again with separator 47 and thereby transports thetransfer paper sheet to medium ejection port 2BY through the transportpath for medium ejection and ejects it to medium delivery section 2BX.In this case, color printer 1 forms the print image by transferring andfixing the toner image of the base colors on the surface of the transferpaper sheet, and then transferring and fixing the toner image of whiteas the special color. Thus, the base colors can be coated with white inthe print image. Because the transfer with the transfer paper sheet ismade by bringing the print image on that surface into contact with thesurface of a T-shirt, color printer 1 can make white serve as afoundation for the base colors when the print image is transferred ontoa T-shirt by way of the transfer paper sheet. Thereby, thanks to whiteserving as the foundation for the base colors, color printer 1 canrepresent the print image with the base colors as clear as theiroriginal colors no matter which of a white T-shirt and a T-shirt ofanother color is used as the medium on which the print image istransferred.

On the other hand, in the situation where first image formation unit 10holding clear toner is attached to color printer 1 and plain paper ofwhite or another color is loaded in media cassette 41 as print medium 5,for example, the printer forms a print image by transferring and fixingtoner images of the base colors to the surface of a plain paper sheetand then transferring and fixing thereto a toner image of clear as thespecial color, as in the case of forming a print image on the surface ofa transfer paper sheet. Thereby, color printer 1 can gloss the basecolors by coating the base colors with the color of clear in the printimage formed on the surface of the plain paper sheet. In this way, colorprinter 1 can form a print image in the bordered printing mode on thesurface of any of various print media 5, for example, such that the basecolors and the special color are laid in the order predefined accordingto the type of print medium 5.

Meanwhile, as described above, when color printer 1 forms a print imagerepresented with the base colors and white as the special color on thesurface of a plain paper sheet as print medium 5, the special colorserves as the foundation for the base colors. Further, when colorprinter 1 forms a print image represented with the base colors and whiteas the special color on the surface of a transfer paper sheet as printmedium 5, the special color is located on the base colors on thetransfer paper sheet, but as in the above case, the special color servesas the foundation for the base colors in the state where the print imageis transferred on the surface of a T-shirt. Furthermore, when colorprinter 1 forms a print image represented with the base colors and thecolor of clear as the special color on the surface of a plain papersheet as print medium 5, the special color is located on the basecolors, and the base colors serve as the foundation for the specialcolor. Hence, in the following description, depending on the type ofprint medium 5 on which a print image is to be formed and the type ofthe special color used to represent the print image, white as thespecial color which serves as the foundation for the base colors in theprint image and the base colors which serve as the foundation for thecolor of clear as the special color in the print image are also called aground color as appropriate, and the base colors which are located onwhite as the special color serving as the foundation for the base colorsin the print image and the color of clear as the special color which islocated on the base colors serving as the foundation for the specialcolor are also called an upper color as appropriate.

(1-2) Circuit Configuration of the Color Printer

Next, the circuit configuration of color printer 1 is described usingFIG. 2. In color printer 1, storage unit 51 such as a hard disc drive ora ROM (Read Only Memory), a memory (not illustrated) such as a RAM(Random Access Memory) serving as a work area for first controller 50,and manipulation panel 4 described above are connected to firstcontroller 50, such as a CPU (Central Processing Unit) or amicroprocessor. Moreover, first image input unit 52 and head controller53 are connected to first controller 50. First image input unit 52 isconfigured to load image data of an image to be printed from the outsideand generate print image data of the print image having an image sizeslightly smaller than the size of the print medium for use in borderedprinting, for example. Head controller 53 is configured to control firstto fifth LED heads 25 to 29 described above. Note that, first imageinput unit 52 is capable of loading image data of an image to be printedthat is stored in, for example, an external memory such as a USB(Universal Serial Bus) memory or a memory card attached to color printer1. Alternatively, first image input unit 52 is also capable of loadingimage data of an image to be printed from, for example, an imagingdevice connected to color printer 1 by wire or wireless, such as adigital still camera or a mobile information terminal equipped with acamera function. Still alternatively, first image input unit 52 is alsocapable of loading image data of an image to be printed from, forexample, an information processing device connected to color printer 1by wire or wireless, such as a personal computer.

First controller 50 is configured to load various programs such as abase program, a first image processing program, and a variety ofapplication programs previously stored in storage unit 51 from thestorage unit to the memory as appropriate, and expand these in thememory. Further, first controller 50 is configured to exert an overallcontrol on color printer 1 according to the various programs thusdeveloped in the memory, and execute predetermined arithmeticprocessing, various processing in response to manipulation commandsinputted through manipulation panel 4, and the like. With thesefunctions, at the time of forming a print image, first controller 50drives image formation section 7, medium supply section 43, and the likefor forming a print image, executes image processing on print image datagiven by first image input unit 52, and sends corrected print image datathus obtained to head controller 53. In this event, based on thecorrected print image data given by first controller 50, head controller53 generates second to fifth head control data corresponding to colorcomponents of cyan, magenta, yellow, and black of the print image, andgenerates first head control data corresponding to a color component ofwhite or clear of the print image. In addition, under control of firstcontroller 50, head controller 53 sends each of first to fifth headcontrol data to a corresponding one of first to fifth LED heads 25 to 29at a predetermined timing. In this way, in first to fifth imageformation units 10 to 14, first controller 50 can drive first to fifthLED heads 25 to 29 to form electrostatic latent images on the surfacesof first to fifth photoconductive drums 20 to 24 based on first to fifthhead control data, and form toner images by developing the electrostaticlatent images with toner. Further, first controller 50 can form a printimage on the surface of print medium 5 as described above based on thetoner images formed by first to fifth image formation units 10 to 14.

Meanwhile, in some color printers, toner images on the surfaces of firstto fifth photoconductive drums 20 to 24 are transferred onto the surfaceof transfer belt 33 while being misaligned relative to their idealtransfer positions depending on factors such as assembly precision ofthe printer. In this case, because the toner images of five colors ontransfer belt 33 are transferred and fixed to the surface of printmedium 5 while being misaligned with each other in color printer 1, suchmisregistration leads to a misregistration of the ground color and theupper color laid one over another in a print image. This eventuallymakes the ground color spread out from under the upper color in an edgeportion and a central portion of the print image. Further, in colorprinter 1, depending on factors such as its assembly precision, there istendency that the misregistration of the ground color and the uppercolor laid one over another in the print image increases and a largerportion of the ground color spreads out from under the upper color inthe case of forming a print image. This happens in such a way that atoner image of a special color on transfer belt 33 is transferred andfixed to the surface of print medium 5. Then toner images of base colorson the belt are transferred and fixed thereto; or in the case of forminga print image in such a way that toner images of the base colors on thebelt are transferred and fixed to the surface of print medium 5 and thena toner image of the special color on the belt is transferred and fixedthereto. This is as compared to the case of forming a print image insuch a way that toner images of the base colors and a toner image of thespecial color on the belt are transferred and fixed to the surface ofprint medium 5 at the same time. Incidentally, in the followingdescription, an image formation method of forming a print image in sucha way that toner images of the base colors and a toner image of thespecial color on transfer belt 33 are transferred and fixed to thesurface of print medium 5 at the same time is also referred to as afirst image formation method. An image formation method of forming aprint image in such a way that toner images of the base colors ontransfer belt 33 are transferred and fixed to a surface of print medium5 and then a toner image of the special color on transfer belt 33 istransferred and fixed thereto is also referred to as a second imageformation method.

To deal with such a phenomenon, color printer 1 previously detects, forexample, the amount of first misregistration estimated to occur betweenthe ground color and the upper color, laid one over another, when aprint image is formed in the bordered printing mode on the surface ofprint medium 5 with the first image formation method and the groundcolor spreads out from under the upper color in this print image. Inaddition, based on the amount of the first misregistration, colorprinter 1 assigns, as appropriate, a block-shaped first pixel searchrange for searching pixels to be corrected in the print image, forexample. Further, based on the amount of the first misregistration andthe image size of the print image, the color printer assigns, asappropriate, a first area detection range for detecting an edge-portionarea to be corrected in an edge portion of the print image for borderedprinting (hereinafter, such an area is also referred to as anedge-portion correction area for bordered mode). The first areadetection range is in the shape of a frame going around the print imagealong the edges of the image. Thus, first controller 50 stores, instorage unit 51, first pixel search range information indicating thefirst pixel search range and first area detection range informationindicating the first area detection range. Besides, color printer 1 alsopreviously detects, for example, the amount of second misregistrationestimated to occur between the ground color and the upper color, laidone over another, when a print image is formed in the bordered printingmode on a surface of print medium 5 with the second image formationmethod and the ground color spreads out from under the upper color inthis print image. In addition, based on the amount of the secondmisregistration, color printer 1 assigns, as appropriate, a block-shapedsecond pixel search range for searching pixels to be corrected in theprint image for bordered printing, for example. Further, based on theamount of the second misregistration and the image size, a second areadetection range in the shape of a frame, going around the print imagealong the edges of the image, is determined for detecting anedge-portion correction area for the bordered mode in an edge portion ofthe print image. Thus, first controller 50 stores, in storage unit 51,second pixel search range information indicating the second pixel searchrange and second area detection range information indicating the secondarea detection range.

Incidentally, the amount of the first misregistration is detected as thefirst misregistration distance represented with pixels and the firstmisregistration direction, for example. When the amount of the firstmisregistration is used for assignment of the first pixel search range,a reference length for the search range assignment is obtained bydoubling the first misregistration distance in the first misregistrationdirection, and the reference length for search range assignment isdivided into a main-direction component length in a main-scanningdirection of the print image and a sub-direction component length in asub-scanning direction. In this way, the first pixel search range isassigned in the shape of a square or a rectangular block whose lengthsin the main-scanning direction and in the sub-scanning direction areequal to the main-direction component length and the sub-directioncomponent length of the reference length for search range assignment,respectively. Meanwhile, when the amount of the first misregistration isused for the assignment of the first area detection range, the firstmisregistration distance in the first misregistration direction isdirectly used as a reference length for detection of the rangeassignment and is divided into a main-direction component length in themain-scanning direction of the print image and a sub-direction componentlength in the sub-scanning direction. In this way, the first areadetection range is assigned in the shape of a frame whose width betweenstrip-shaped portions on one and the other image-edge sides in themain-scanning direction of the print image (hereinafter, such edges arealso referred to as image left/right edges collectively and suchportions are also referred to as left/right strip-shaped portionscollectively) is equal to the main-direction component length of thereference length for detection of the range assignment and whose widthbetween strip-shaped portions on one and the other image-edge sides inthe sub-scanning direction (hereinafter, such edges are also referred toas image top/bottom edges collectively and such portions are alsoreferred to as top/bottom strip-shaped portions collectively) is equalto the sub-direction component length of the reference length fordetection range assignment. In other words, the first area detectionrange is assigned in the shape of a frame whose widths between theleft/right strip-shaped portions and between the top/bottom strip-shapedportions are equal to or different from each other. Besides, the secondpixel search range and the second area detection range are assigned inthe same manner as the first pixel search range and the first areadetection range based on the amount of the second misregistrationdetected as a second misregistration distance represented with pixelsand a second misregistration direction. Note, however, that a portion ofthe ground color spreading out from under the upper color tends to belarger in the second image formation method than in the first imageformation method as described above. Thus, in response to that tendency,the second pixel search range and the second area detection range areassigned so that they may be wider in at least one of the main-scanningdirection and the sub-scanning direction than the first pixel searchrange and the first area detection range.

With the configuration above, upon receiving print image data from firstimage input unit 52 in the formation of a print image, first controller50 executes a first image processing by using the first pixel searchrange, the first area detection range, the second pixel search range,and the second area detection range to prevent the ground color fromspreading out from under the upper color throughout the print image(i.e., in an edge portion and a central portion of the image). In fact,first controller 50 executes the first image processing according to thefirst image processing program stored in storage unit 51 by using theprint image data generated by first image input unit 52. With referenceto FIG. 3, print image data generation processing executed by firstimage input unit 52 is described specifically below, and besides, whilevarious functions that first controller 50 implements according to thefirst image processing program are indicated by functional circuitblocks for the sake of convenience, the first image processing thatfirst controller 50 executes according to the first image processingprogram is described specifically below as the processing executed bythe functional circuit blocks.

In this case, when a command to display a setting screen is made at anytiming by the user through manipulation panel 4, for example, settingunit 61 of first spread-out correction unit 60 retrieves setting screendata from storage unit 51, and sends it to manipulation panel 4 todisplay the setting screen in response to the command. Setting unit 61thereby makes the user input the type of print medium 5 loaded in mediacassette 41 and a color of toner held by first image formation unit 10(i.e., white or clear as the special color) at this time on the settingscreen through manipulation panel 4. Setting unit 61 then detects animage formation method (i.e., any of the first image formation methodand the second image formation method) to be used in the formation of aprint image and the types of the ground color and the upper color. Then,setting unit 61 makes a setting such that all parts of first spread-outcorrection unit 60 (i.e., boundary correction area detector 62, firstedge-portion correction area detector 63, and first correction processor64) execute a processing according to the image formation method and thetypes of the ground color and the upper color thus detected. In thisevent, setting unit 61 also sets first image input unit 52 to generateprint image data of a print image represented with the types of groundcolor and the upper color thus detected. Incidentally, setting unit 61is capable of detecting an image formation method and the types of theground color and the upper color not only upon input on the settingscreen as described above, but also, for example, upon notification froman information processing device connected to color printer 1, such as apersonal computer, if the image data of an image to be printed is givenfrom the image processing device to first image input unit 52. Notethat, hereinbelow, print image data generation processing and firstimage processing applied to the print image data that are executed whena print image in which white serves as the ground color is formed on asurface of a plain paper sheet as print medium 5 according to thesetting made by setting unit 61 are described specifically. Thendescribed are the print image data generation processing and first imageprocessing applied to the print image data that are executed when aprint image in which white serves as the ground color is formed on asurface of a transfer paper sheet as print medium 5 according to thesetting made by setting unit 61, and the print image data generationprocessing and first image processing applied to the print image datathat are executed when a print image in which the base colors serve asthe ground color (that is, the color of clear serves as the upper color)is formed on a surface of a plain paper sheet as print medium 5according to the setting made by setting unit 61. The events aredescribed in this order.

In the case where a print image, in which white serves as the groundcolor, is formed on the surface of a plain paper sheet, upon loadingimage data of an image to be printed from the outside, first image inputunit 52 generates print image data of the print image represented withthe colors of cyan, magenta, yellow, black, and white based on theloaded image data. In this event, first image input unit 52 stores, inthe print image data for every pixel of the print image, five kinds ofpixel values represented by normalizing the densities of cyan, magenta,yellow, black, and white into values from “0” to “255” respectivelybased on the pattern of the print image. In fact, the pixel value ofcyan for each pixel becomes “0” when the color of cyan is not used torepresent the pixel, and becomes a value larger than “0” according toits density when the color of cyan is used to represent the pixel. Thesame holds for the pixel values of magenta, yellow, black, and white foreach pixel. Note, however, that, in order to make white serve as theground color only for a base color portion in the print image, for everypixel of the print image, first image input unit 52 sets the pixel valueof white at a value larger than “0,” more preferably at “255” indicatingthe highest density for the purpose of fully exploiting its function asthe ground color if at least one of the pixel values of cyan, magenta,yellow, and black is equal to a value larger than “0,” and sets thepixel value of white at “0” if all of the pixel values of cyan, magenta,yellow, and black are equal to “0.” Accordingly, in the print image, acolored area is an area including only pixels in each of which the pixelvalue of white is larger than “0” and at least one of the pixel valuesof cyan, magenta, yellow, and black is larger than “0.” Further, in theprint image, a colorless area is an area including only pixels in eachof which all the pixel values of cyan, magenta, yellow, black, and whiteare equal to “0.” First image input unit 52 generates the print imagedata in this manner and sends it to boundary correction area detector62.

Upon receiving the print image data from first image input unit 52,boundary correction area detector 62 retrieves first pixel search rangeinformation from storage unit 51 and executes boundary correction areadetection processing according to the setting made by setting unit 61.In this event, as illustrated in FIG. 4, while shifting first pixelsearch range SE1 in the main-scanning direction or in the sub-scanningdirection sequentially on a pixel-by-pixel basis on print image IM1which is based on the print image data, boundary correction areadetector 62 makes every pixel in print image IM1 positioned at thecenter of first pixel search range SE1 sequentially one at a time todesignate the pixel as focused pixel P51. First pixel search range SE1is indicated by the first pixel search range information and is formedof a square of five pixels (in the main-scanning direction)×five pixels(in the sub-scanning direction), for example. In addition, every timeboundary correction area detector 62 designates each pixel as focusedpixel PS1 on print image IM1 one at a time, it judges whether or notboth conditions where focused pixel PS1 is a pixel of colorless area AR1and where at least one of pixels PN1 located around focused pixel PS1 infirst pixel search range SE1 (hereinafter, such pixels are also referredto as neighboring pixels) is a pixel of colored area AR2 are satisfiedon the basis of the five kinds of pixel values of focused pixel PS1 andthe five kinds of pixel values of each of neighboring pixels PN1. As aresult of the judgment, if focused pixel PS1 is a pixel of colored areaAR1 and at least one of neighboring pixels PN1 is a pixel of coloredarea AR2, boundary correction area detector 62 judges that focused pixelPS1 at this time is a pixel to be corrected for boundary correction(hereinafter, such pixel is also referred to as a boundary correctionpixel). In contrast, if focused pixel PS1 is a pixel of colorless areaAR1 but all of neighboring pixels PN1 are pixels in colorless area AR1as well, boundary correction area detector 62 judges that focused pixelPS1 at this time is a pixel not to be corrected (non-correction pixel).Further, if all of focused pixel PS1 and neighboring pixels PN1 arepixels in colored area AR2, boundary correction area detector 62 judgesthat focused pixel PS1 at this time is a non-correction pixel as in theabove case. In this manner, based on the judgment result, boundarycorrection area detector 62 detects a boundary area to be corrected(boundary correction area) which is a boundary portion between colorlessarea AR1 and colored area AR2 in print image IM1 and is formed ofboundary correction pixels. Note that boundary correction area detector62 generates boundary correction area detection data indicating aboundary correction area while judging, one at a time, whether each ofpixels in print image IM1 is a boundary correction pixel or anon-correction pixel. Specifically, boundary correction area detector 62stores data in the boundary correction area detection data such that itassociates a value of “1” indicating a boundary correction pixel with apixel in print image IM1 if judging that the pixel is a boundarycorrection pixel, and such that it associates a value of “0” indicatinga non-correction pixel with a pixel in print image IM1 if judging thatthe pixel is a non-correction pixel. Upon detecting a boundarycorrection area, boundary correction area detector 62 sends firstedge-portion correction area detector 63 the boundary correction areadetection data together with the print image data.

Upon receiving the boundary correction area detection data together withthe print image data from boundary correction area detector 62, firstedge-portion correction area detector 63 retrieves first area detectionrange information from storage unit 51 and executes first edge-portioncorrection area detection processing according to the setting made bysetting unit 61. In this event, as illustrated in FIG. 5, firstedge-portion correction area detector 63 designates every pixel in printimage IM1 based on the print image data as a focused pixel sequentiallyone at a time. Then, every time first edge-portion correction areadetector 63 designates each pixel as a focused pixel on print image IM1one at a time, it judges whether or not the focused pixel is a pixel ofcolored area AR2 and also whether or not the focused pixel is a pixelwithin first area detection range DE1 on the basis of first areadetection range DE1 and the five kinds of pixel values of the focusedpixel, first area detection range DE1 being indicated by the first areadetection range information and having left/right strip-shaped portionsof the same width and top/bottom strip-shaped portions of the samewidth, for example. Note that first edge-portion correction areadetector 63 may judge that a focused pixel is a pixel within first areadetection range DE1 if the coordinates of the focused pixel satisfy atleast one of four kinds of conditions represented by the followingformulae (1) to (4):

x<W1  (1);

y<W1  (2);

x≧X1−W1  (3); and

y≧Y1−W1  (4),

where: X1 and Y1 indicate the horizontal size and the vertical size ofprint image IM1 represented with the number of pixels in themain-scanning direction and in the sub-scanning direction, respectively,with the left upper corner of the print image used as point of originOP1 (0, 0). W1 indicates the width of each of the left/rightstrip-shaped portions and the top/bottom strip-shaped portions of firstarea detection range DE1 represented by the number of pixels thereof;and (x, y) indicates the coordinates of the focused pixel. Then, asillustrated in FIG. 6, if the focused pixel is a pixel of colored areaAR2 and is also a pixel within first area detection range DE1, firstedge-portion correction area detector 63 judges that this focused pixelis a pixel to be corrected for image edge-portion correction(hereinafter, such pixel is also referred to as an edge-portioncorrection pixel). In contrast, if the focused pixel is a pixel ofcolorless area AR1, first edge-portion correction area detector 63judges that this focused pixel is a non-correction pixel irrespective ofwhether or not this focused pixel is a pixel within first area detectionrange DE1. Further, if the focused pixel is a pixel of colored area AR2but is a pixel outside first area detection range DE1, firstedge-portion correction area detector 63 also judges that this focusedpixel is a non-correction pixel. In this manner, based on the judgmentresult, first edge-portion correction area detector 63 detects theedge-portion correction area for bordered mode AR3, which extends alongthe edges of the image formed by edge-portion correction pixels, incolored area AR2 located in left/right edge portions and top/bottom edgeportions of print image IM1. Incidentally, FIG. 6 illustrates an examplewhere all of the image left/right edge portions and the image top/bottomedge portions are colored area AR2 and thus first area detection rangeDE1 overlapping these portions are detected directly as an edge-portioncorrection area for bordered mode AR3. Note that first edge-portioncorrection area detector 63 generates edge-portion correction areadetection data indicating an edge-portion correction area for borderedmode AR3 while judging, one at a time, whether each of the pixels inprint image IM1 is an edge-portion correction pixel or a non-correctionpixel. Specifically, first edge-portion correction area detector 63stores data in the edge-portion correction area detection data such thatit associates a value of “1” indicating an edge-portion correction pixelwith a pixel in print image IM1 if judging that the pixel is anedge-portion correction pixel. It associates a value of “0” indicating anon-correction pixel with a pixel in print image IM1 if judging that thepixel is a non-correction pixel. Upon detecting an edge-portioncorrection area for bordered mode AR3, first edge-portion correctionarea detector 63 sends first correction processor 64 the edge-portioncorrection area detection data together with the print image data andthe boundary correction area detection data.

Upon receiving the boundary correction area detection data and theedge-portion correction area detection data together with the printimage data from first edge-portion correction area detector 63, firstcorrection processor 64 retrieves first pixel search range informationfrom storage unit 51 and executes first correction processing accordingto the setting made by setting unit 61. In this event, as illustrated inFIG. 7, while shifting first pixel search range SE1 (not illustrated inFIG. 7) indicated by the first pixel search range information in themain-scanning direction or in the sub-scanning direction sequentially ona pixel-by-pixel basis on print image IM1 which is based on the printimage data, first correction processor 64 designates every pixel inprint image IM1 as focused pixel PS1 at the center of first pixel searchrange SE1 sequentially one at a time, for example. In addition, everytime first correction processor 64 designates each pixel as a focusedpixel PS1 on print image IM1 one at a time, it judges whether or notfocused pixel PS1 is an edge-portion correction pixel and whether or notthe focused pixel is a boundary correction pixel on the basis of theedge-portion correction area detection data and the boundary correctionarea detection data. As a result of the judgment, if focused pixel PS1is an edge-portion correction pixel, first correction processor 64replaces, with “0,” only the pixel value of white out of the five kindsof pixel values of this focused pixel PS1 (i.e., edge-portion correctionpixel). Meanwhile, if focused pixel PS1 is a boundary correction pixel,out of the pixel values exclusive of the pixel value of white among thefive kinds of pixel values of focused pixel PS1 (i.e., boundarycorrection pixel), first correction processor 64 changes the pixel valueof cyan from its original value of “0” to the largest value among thepixel values of cyan that neighboring pixels PN1 in first pixel searchrange SE1 respectively have. In the same way, first correction processor64 changes each of the pixel values of magenta, yellow, and black thatthis focused pixel PS1 (i.e., a boundary correction pixel) has from itsoriginal value of “0” to the largest value among the pixel values of thecorresponding color that neighboring pixels PN1 in first pixel searchrange SE1 respectively have. Note that, if focused pixel PS1 is anon-correction pixel (that is, focused pixel PS1 is neither anedge-portion correction pixel nor a boundary correction pixel), firstcorrection processor 64 leaves the five kinds of pixel values of thisfocused pixel PS1 unchanged.

Thereby, first correction processor 64 can correct print image IM1 sothat edge-portion correction area for bordered mode AR3 extending alongthe edges of print image IM1 may be represented only with the uppercolor, and thus, in an edge portion of print image IM1, it can make thewidth of the ground color narrower than the width of the upper color,laid over the ground color, such that the area of the ground colorretreats toward the center of the image from the image edges. Inaddition, first correction processor 64 can correct print image IM1 sothat boundary correction area AR4 in a central portion of print imageIM1 may be represented only with the upper color, and thus it can makethe width of the upper color wider than the width of the ground colorlaid under the upper color in a central portion of print image IM1.Then, first correction processor sends the print image data of printimage IM1, whose edge-portion correction area for bordered mode AR3 andboundary correction area AR4 are corrected, to output image processor 65as corrected print image data. Incidentally, upon receipt of thecorrected print image data from first correction processor 64, outputimage processor 65 performs a predetermined processing, such as a tonecorrection processing and a value reduction processing using a ditheringtechnique, an error diffusion technique, or the like, on the correctedprint image data, and sends the resultant data to subsequent headcontroller 53.

In this manner, as illustrated in FIG. 8, color printer 1 forms printimage IM1 in the state where the edge-portion correction area forbordered mode AR3 and boundary correction area AR4 are corrected, in aprint area slightly smaller than the surface of print medium 5 and inthe bordered printing mode where a fringe portion of the print medium onthe surface thereof is entirely left unprinted. In the meantime, aconventional color printer does not perform the first image processingat all on the print image data as done in embodiment 1=. Hence, when aprint image in which white serves as ground color GC1 is formed on asurface of print medium 5, for example, upper color UC1 having a widthequal to ground color GC1 is laid over the ground color, as illustratedin FIG. 9A. Thus, if upper color UC1 and ground color GC1 laid one overanother in a print image on print medium 5 are misaligned with eachother in the conventional color printer, ground color GC1 spreads outfrom under upper color UC1, as illustrated in FIGS. 9B and 9C. As aresult, in the conventional color printer, ground color GC1 which shouldbe originally hidden under upper color UC1 and invisible in the printimage turns visible and stands out, which deteriorates the quality ofthe print image. On the other hand, color printer 1 according toembodiment 1 corrects edge-portion correction area for bordered mode AR3and boundary correction area AR4 in print image IM1 based on print imagedata so that, in prospect of such misregistration, the width of uppercolor UC2 laid over ground color GC2 may be widened relative to thewidth of ground color GC2, as illustrated in FIG. 10A. Thus, when printimage IM1 in which white serves as ground color GC2 is formed on asurface of print medium 5 in color printer 1, for example, it ispossible to lay upper color UC2 with a width wider than ground color GC2over the ground color. By doing so, even if upper color UC2 and groundcolor GC2 laid one over another in print image IM1 on print medium. 5are misaligned with each other in color printer 1, it is possible toprevent ground color GC2 from spreading out from under upper color UC2,as illustrated in FIGS. 10B and 10C. Accordingly, in color printer 1,ground color GC2 which should be originally hidden under upper color UC2and invisible in the print image can be kept invisible even when thesecolors are misaligned with each other, so that the deterioration in thequality of print image IM1 can be prevented.

Next, in the case where print image IM1 in which white as the specialcolor serves as the ground color is formed on a surface of a transferpaper sheet, the configuration of the print image data itself of printimage IM1 is no different from the configuration of the print image datadescribed above; thus, upon loading image data of an image to be printedfrom the outside, first image input unit 52 generates print image datasimilar to the above print image data based on the loaded image data,and sends it to boundary correction area detector 62. Upon receiving theprint image data from first image input unit 52, boundary correctionarea detector 62 retrieves second pixel search range information fromstorage unit 51 in this case according to the setting made by settingunit 61, but executes the boundary correction area detection processingas in the above case using the second pixel search range information.Boundary correction area detector 62 thereby detects boundary correctionarea AR4 in print image IM1 based on the print image data, and sendsfirst edge-portion correction area detector 63 the boundary correctionarea detection data together with the print image data. Upon receivingthe boundary correction area detection data together with the printimage data from boundary correction area detector 62, first edge-portioncorrection area detector 63 retrieves second area detection rangeinformation from storage unit 51 in this case according to the settingmade by setting unit 61, but executes the first edge-portion correctionarea detection processing as in the above case using the second areadetection range information. First edge-portion correction area detector63 thereby detects edge-portion correction area for bordered mode AR3 inprint image IM1 based on the print image data, and sends firstcorrection processor 64 the edge-portion correction area detection datatogether with the print image data and the boundary correction areadetection data. Upon receiving the boundary correction area detectiondata and the edge-portion correction area detection data together withthe print image data from first edge-portion correction area detector63, first correction processor 64 retrieves second pixel search rangeinformation from storage unit 51, in this case according to the settingmade by setting unit 61, but executes the first correction processing asin the above case using the second pixel search area information. Firstcorrection processor 64 thereby corrects boundary correction area AR4 aswell as edge-portion correction area for bordered mode AR3 of printimage IM1. First correction processor 64 then sends the print image dataof print image IM1 thus corrected to output image processor 65 ascorrected print image data.

In the meantime, when print image IM1 is formed on a surface of atransfer paper sheet in color printer 1 based on the corrected printimage data, white having a width narrower than the width of the basecolors is laid over the base colors on the transfer paper sheet andhence the base colors spread out from under white. However, if printimage IM1 is transferred onto a T-shirt by way of the transfer papersheet, white serves as the ground color and the base colors, being widerthan white, are laid over white as described above. Thereby, in colorprinter 1, even if the upper color and the ground color laid one overanother in print image IM1 on the transfer paper sheet are misalignedwith each other, it is possible to prevent the ground color fromspreading out from under the upper color in the state where print imageIM1 is transferred on a T-shirt. Accordingly, in color printer 1, theground color which should be originally hidden under the upper color andinvisible on a T-shirt being a final target for the formation of printimage IM1 can be kept invisible even when these colors are misalignedwith each other, so that the deterioration in the quality of print imageIM1 can be prevented.

Next, in the case where print image IM1 in which the base colors serveas the ground color (that is, the color of clear as the special colorserves as the upper color) is formed on the surface of a plain papersheet, upon loading image data of an image to be printed from theoutside, first image input unit 52 generates print image data of printimage IM1 represented with the colors of cyan, magenta, yellow, black,and clear based on the loaded image data. In this event, first imageinput unit 52 stores, in the print image data for every pixel of printimage IM1, five kinds of pixel values represented by normalizing thedensities of cyan, magenta, yellow, black, and clear into values from“0” to “255” respectively. Note that, as in the case of the print imagein which white serves as the ground color described above, each of thepixel values of cyan, magenta, yellow, and black for each pixel becomeswhen the corresponding color is not used to represent the pixel, andbecomes a value larger than “0” according to its density when thecorresponding color is used to represent the pixel. Further, in order tomake the color of clear serve as the upper color for glossing the basecolors in print image IM1, for every pixel of print image IM1, firstimage input unit 52 sets the pixel value of clear at a value larger than“0,” more preferably at “255” indicating the highest density for thepurpose of achieving sufficient gloss if at least one of the pixelvalues of cyan, magenta, yellow, and black is equal to a value largerthan “0,” and sets the pixel value of clear at “0” if all of the pixelvalues of cyan, magenta, yellow, and black are equal to “0.”Accordingly, in print image IM1 in which the base colors serve as theground color, a colored area is an area including only pixels in each ofwhich the pixel value of clear is larger than “0” and at least one ofthe pixel values of cyan, magenta, yellow, and black is larger than “0,”and a colorless area is an area including only pixels in each of whichall the pixel values of cyan, magenta, yellow, black, and clear areequal to “0.” First image input unit 52 generates the print image datain this manner and sends it to boundary correction area detector 62.

Upon receiving the print image data from first image input unit 52,boundary correction area detector 62 retrieves second pixel search rangeinformation from storage unit 51 according to the setting made bysetting unit 61 and executes the boundary correction area detectionprocessing as in the above case. Boundary correction area detector 62thereby detects boundary correction area AR4 in print image IM1 based onthe print image data, and sends first edge-portion correction areadetector 63 the boundary correction area detection data together withthe print image data. Upon receiving the boundary correction areadetection data together with the print image data from boundarycorrection area detector 62, first edge-portion correction area detector63 retrieves second area detection range information from storage unit51 according to the setting made by setting unit 61 and executes thefirst edge-portion correction area detection processing as in the abovecase. First edge-portion correction area detector 63 thereby detects theedge-portion correction area for bordered mode AR3, which extends alongthe edges of the image, in print image IM1 based on the print imagedata, and sends first correction processor 64 the edge-portioncorrection area detection data together with the print image data andthe boundary correction area detection data. Upon receiving the boundarycorrection area detection data and the edge-portion correction areadetection data together with the print image data from firstedge-portion correction area detector 63, first correction processor 64retrieves second pixel search range information from storage unit 51according to the setting made by setting unit 61 and executes a firstcorrection processing. In this event, as in the above case, whileshifting the second pixel search range sequentially on a pixel-by-pixelbasis on print image IM1, first correction processor 64 designates everypixel in print image IM1 as a focused pixel sequentially one at a time,and judges whether or not the focused pixel is an edge-portioncorrection pixel and whether or not the focused pixel is a boundarycorrection pixel. As a result of the judgment, if the focused pixel isan edge-portion correction pixel, out of the five kinds of pixel valuesof this focused pixel (i.e., edge-portion correction pixel), firstcorrection processor 64 changes each of the pixel values of cyan,magenta, yellow, and black, excluding the pixel value of clear from itsoriginal value larger than “0,” to “0” because the base colors serve asthe ground color in print image IM1. Thereby, first correction processor64 can correct print image IM1 so that edge-portion correction area forbordered mode AR3 extending along the edges of print image IM1 may berepresented only with the color of clear as the upper color, and thus,in an edge portion of the image, it can make the width of the basecolors as the ground color narrower than the width of the color of clearas the upper color, laid over the ground color, such that the area ofthe ground color retreats toward the center of the image from the imageedges. In addition, if the focused pixel is a boundary correction pixel,out of the five kinds of pixel values of this focused pixel (i.e.,boundary correction pixel), first correction processor 64 changes onlythe pixel value of clear from its original value of “0” to a valuelarger than “0,” for example, “255.” Thereby, first correction processor64 can make the width of the color of clear as the upper color widerthan the width of the base colors as the ground color laid under theupper color in a central portion of print image IM1. Then, firstcorrection processor 64 sends the print image data of print image IM1corrected in the above manner to output image processor 65 as correctedprint image data. Thus, when print image IM1 represented with the basecolors as the ground color and the color of clear as the upper color isformed on the surface of print medium 5 in color printer 1, it ispossible to lay the color of clear wider than the ground color laid overthe ground color. By doing so, even if the base colors and the color ofclear laid one over another in print image IM1 on print medium 5 aremisaligned with each other in color printer 1, it is possible to preventthe base colors from spreading out from under the color of clear.Accordingly, in color printer 1, even if the color of clear and the basecolors are misaligned with each other in print image IM1, it is possibleto avoid the generation of base color portions that cannot be coatedwith the color of clear and gloss the base colors exactly, and thus toprevent the deterioration in the quality of print image IM1.

(1-3) First Image Processing

Next, with the flowcharts illustrated in FIGS. 11 to 13, a descriptionis given of boundary correction area detection processing procedure RT1,first edge-portion correction area detection processing procedure RT2,and first correction processing procedure RT3 that first controller 50executes as part of a first image processing procedure according to thefirst image processing program. Upon receiving print image data fromfirst image input unit 52, first controller 50 starts boundarycorrection area detection processing procedure RT1 illustrated in FIG. 1according to the first image processing program. Upon starting boundarycorrection area detection processing procedure RT1, in step SP1, firstcontroller 50 designates one of the pixels in print image IM1 as focusedpixel PS1, and judges whether or not both conditions where this focusedpixel PS1 is a pixel of colorless area AR1 and where any pixel ofcolored area AR2 exists within a pixel search range (i.e., amongneighboring pixels PN1 in first pixel search range SE1 or the secondpixel search range which are located around focused pixel PS1) aresatisfied. If a positive result is obtained in step SP1, it indicatesthat the width of the upper color laid over the ground color can be madewider than the width of the ground color in a central portion of printimage IM1 by making such a correction that focused pixel PS1 may berepresented with the upper color. Thus, if a positive result is obtainedin step SP1, first controller 50 proceeds to step SP2 to judge that thisfocused pixel PS1 is a boundary correction pixel of boundary correctionarea AR4, and proceeds to next step sp3. In contrast, if a negativeresult is obtained in step SP1, it indicates that focused pixel PS1 is apixel relatively away from a boundary between colorless area AR1 andcolored area AR2, and therefore the width of the upper color laid overthe ground color cannot be made wider than the width of the ground colorin the central portion of print image IM1 even by making such acorrection that focused pixel PS1 may be represented with the uppercolor. Thus, if a negative result is obtained in step SP1, firstcontroller 50 proceeds to step SP4 to judge that this focused pixel PS1is a non-correction pixel outside boundary correction area AR4, andproceeds to step SP3. In step SP3, first controller 50 judges whether ornot the judgment on all the pixels in print image IM1 is over, and goesback to step SP1 if a negative result is obtained. When first controller50 finishes judging all the pixels in print image IM1 to be either aboundary correction pixel or a non-correction pixel, it detects boundarycorrection area AR4 based on the judgment result. Then, if a positiveresult is obtained in step SP3, first controller 50 proceeds to nextstep SP5 to terminate boundary correction area detection processingprocedure RT1.

When first controller 50 finishes boundary correction area detectionprocessing procedure RT1, it subsequently starts first edge-portioncorrection area detection processing procedure RT2 illustrated in FIG.12 according to the first image processing program. Upon starting firstedge-portion correction area detection processing procedure RT2, in stepSP11, first controller 50 designates one of the pixels in print imageIM1 as a focused pixel, and judges whether or not this focused pixel isa pixel of colored area AR2 and also a pixel within an area detectionrange (i.e., first area detection range DE1 or the second area detectionrange) extending along the edges of the image. If a positive result isobtained in step SP11, it indicates that the width of the ground colorcan be made narrower than the width of the upper color, laid over theground color, in an edge portion of print image IM1 such that the areaof the ground color retreats toward the center of the image from theimage edges by making such a correction that the focused pixel may berepresented with the upper color. Thus, if a positive result is obtainedin step SP11, first controller 50 proceeds to step SP12 to judge thatthis focused pixel is an edge-portion correction pixel of theedge-portion correction area for bordered mode AR3, and proceeds to nextstep SP13. In contrast, if a negative result is obtained in step SP11,it indicates that the focused pixel is a pixel relatively away from theedge portion of print image IM1, and therefore the width of the groundcolor cannot be made narrower than the width of the upper color, laidover the ground color, in the edge portion of print image IM1 such thatthe area of the ground color retreats toward the center of the imagefrom the image edges even if such a correction is made that the focusedpixel may be represented with the upper color. Thus, if a negativeresult is obtained in step SP11, first controller 50 proceeds to stepSP14 to judge that this focused pixel is a non-correction pixel outsidethe edge-portion correction area for bordered mode AR3, and proceeds tostep SP13. In step SP13, first controller 50 judges whether or not thejudgment on all the pixels in print image IM1 is over, and goes back tostep SP11 if a negative result is obtained. When first controller 50finishes judging all the pixels in print image IM1 to be either anedge-portion correction pixel or a non-correction pixel, it detects theedge-portion correction area for bordered mode AR3 based on the judgmentresult. Then, if a positive result is obtained in step SP13, firstcontroller 50 proceeds to next step SP15 to terminate first edge-portioncorrection area detection processing procedure RT2.

When first controller 50 finishes first edge-portion correction areadetection processing procedure RT2, it subsequently starts firstcorrection processing procedure RT3 illustrated in FIG. 13 according tothe first image processing program. Upon starting first correctionprocessing procedure RT3, in step SP21, first controller 50 designatesone of the pixels in print image IM1 as focused pixel PS1, and judgeswhether or not this focused pixel PS1 is an edge-portion correctionpixel. If a positive result is obtained, first controller 50 proceeds tostep SP22 to correct the edge-portion correction area for bordered modeAR3 such that the pixel value of the ground color of the edge-portioncorrection pixel is replaced with “0,” and then proceeds to the nextstep SP23. In contrast, if focused pixel PS1 is any of a boundarycorrection pixel and a non-correction pixel, and thus a negative resultis obtained in step S21, first controller 50 proceeds to step SP24 tojudge whether or not this focused pixel PS1 is a boundary correctionpixel. If a positive result is obtained in SP24, first controller 50proceeds to step SP25 to correct boundary correction area AR4 such thatthe pixel value of the upper color of the boundary correction pixel isreplaced with a value larger than “0,” and then proceeds to next stepSP23. On the other hand, if focused pixel PS1 is a non-correction pixelwhich should be excluded from the correction target and a negativeresult is obtained in step SP23, first controller 50 proceeds to stepSP23. In step SP23, first controller 50 judges whether or not thecorrection on the edge-portion correction area for bordered mode AR3 andboundary correction area AR4 in print image IM1 is over. If a negativeresult is obtained in step SP23 because there is a pixel not yet judgedto be an edge-portion correction pixel nor judged to be a boundarycorrection pixel or not and therefore the correction on edge-portioncorrection area for bordered mode AR3 and boundary correction area AR4is not over, first controller 50 goes back to step SP21. Then, if apositive result is obtained in step SP23 because the correction onedge-portion correction area for bordered mode AR3 and boundarycorrection area AR4 is over, first controller 50 proceeds to next stepSP26 to terminate first correction processing procedure RT3.

(1-4) Operation and Effect of Embodiment 1

In color printer 1 having the above configuration, first controller 50loads print image data, and detects the edge-portion correction area forbordered mode AR3 in an edge portion of print image IM1 based on theprint image data. The edge-portion correction area for bordered modeextends along the edges of the image represented with the ground colorand the upper color laid one over another. Then, in color printer 1,first controller 50 corrects print image IM1 based on the print imagedata so that edge-portion correction area for bordered mode AR3 may berepresented only with the upper color, and thereby generates correctedprint image data.

With the above configuration, color printer 1 can make the width of theground color narrower than the width of the upper color, laid over theground color, in the edge portion of print image IM1 based on the printimage data such that the area of the ground color retreats toward thecenter of the image from the image edges. Accordingly, even if theground color and the upper color laid one over another are misalignedwith each other in an edge portion of the image when print image IM1 isformed on a surface of print medium 5 in color printer 1, it is possibleto avoid a situation where the ground color spreads out from under theupper color on the surface of print medium 5 (or on a T-shirt on whichprint image IM1 is eventually formed), that is, avoid a visiblemisregistration of the upper color and the ground color, and thus toprevent the deterioration in the quality of print image IM1.

In addition, in color printer 1, first controller 50 detects boundarycorrection area AR4 adjacent to colored area AR2 in a central portion ofprint image IM1 based on print image data, and corrects boundarycorrection area AR4 so that this area may be represented with the uppercolor. By doing so, color printer 1 can make the width of the uppercolor in colored area AR2 wider than the width of the ground color laidunder the upper color in the central portion of print image IM1 based onthe print image data. Accordingly, in color printer 1, it is alsopossible to avoid a situation where the ground color spreads out fromunder the upper color in a central portion of print image IM1 when printimage IM1 is formed on a surface of print medium 5, and thus to preventthe deterioration in the quality of print image IM1 further reliably.Moreover, in color printer 1, first controller 50 corrects boundarycorrection area AR4 such that, for each pixel of boundary correctionarea AR4, the pixel value of the upper color that this pixel has isreplaced with the largest value among the pixel values of the uppercolor that pixels in a pixel search range, including the pixel as acenter pixel, respectively have. Accordingly, in a central portion ofthe image, color printer 1 can expand a portion of colored area AR2,being a boundary with colorless area AR1, while hardly changing thecolor thereof. Thus, color printer 1 can also prevent the deteriorationin the image quality which would otherwise be caused if the upper colorportion of colored area AR2 expanded by the correction on boundarycorrection area AR4 turns to a color significantly different from itsoriginal color.

Moreover, color printer 1 stores first area detection range DE1 instorage unit 51 as first area detection range information, first areadetection range DE1 having a width assigned according to the amount ofthe first misregistration of the ground color and the upper color in thecase of forming print image IM1 on a surface of print medium 5 with thefirst image formation method, and stores a second area detection rangein storage unit 51 as second area detection range information. Thesecond area detection range has a width assigned according to the amountof the second misregistration of the ground color and the upper color inthe case of forming print image IM1 on a surface of print medium 5 withthe second image formation method. Further, when color printer 1 formsprint image IM1 with the first image formation method, first controller50 detects the edge-portion correction area for bordered mode AR3 infirst area detection range DE1 extending along the edges of the image.and corrects it in print image IM1 based on the print image data.Furthermore, when color printer 1 forms print image IM1 with the secondimage formation method, first controller 50 detects the edge-portioncorrection area for bordered mode AR3 in the second area detection rangeextending along the edges of the image and corrects it in print imageIM1 based on print image data. Accordingly, irrespective of which of thefirst image formation method and the second image formation method colorprinter 1 uses to form print image IM1 on a surface of print medium 5,color printer 1 can narrow the width of the ground color in an edgeportion of print image IM1 based on print image data such that the areaof the ground color retreats toward the center of the image from theimage edges by the amount of correction according to the amount of firstmisregistration or the amount of second misregistration. Thus, even ifthe amount of misregistration of the ground color and the upper colorvaries depending on which method is used to form print image IM1 on asurface of print medium 5, the color printer can adequately avoid asituation where the ground color spreads out from under the upper colorin print image IM1 on the surface of print medium 5 (or on a T-shirt onwhich print image IM1 is eventually formed), and thus prevent thedeterioration in the quality of print image IM1.

(2) Embodiment 2 (2-1) Internal Configuration of Color Printer

Next, a description is given of the internal configuration of colorprinter 70 (FIG. 1) according to embodiment 2. Color printer 70 is notonly capable of forming a print image on the surface of print medium 5in the bordered printing mode, but also capable of forming a print imagethereon in the borderless printing mode where the whole front surface ofprint medium 5 is used as a print area without any border portion lefton the surface. Note, however, that, although the circuit configurationof color printer 70, to be described later, differs from the circuitconfiguration of color printer 1 according to embodiment 1 describedabove in order to enable the formation of a print image in theborderless printing mode, the internal configuration of color printer 70is the same as the internal configuration of color printer 1 accordingto embodiment 1. Accordingly, the internal configuration of colorprinter 70 according to embodiment 2 is understood with reference to thedescription on the internal configuration of color printer 1 accordingto embodiment 1 described with FIG. 1, and is therefore not describedhere.

(2-2) Circuit Configuration of Color Printer

Next, the circuit configuration of color printer 70 is described withFIG. 14 in which portions that are corresponding to those of FIG. 2 aregiven reference numerals that are the same as those of FIG. 2. Colorprinter 70 has the same configuration as in the case of embodiment 1except that second controller 71 such as a CPU or a microprocessor,storage unit 72 such as a hard disc drive or a ROM, and second imageinput unit 73 are provided in place of first controller 50, storage unit51, and first image input unit 52 according to embodiment 1 describedabove. Thus, second controller 71 is configured to load variousprograms, such as a base program and a variety of application programspreviously stored in storage unit 72, from the storage unit to a memory(not illustrated) as appropriate, and expand these in the memory.Further, second controller 71 is configured to exert an overall controlon color printer 70 according to the various programs thus developed inthe memory, and execute a predetermined arithmetic processing, thatincludes various processing in response to manipulation commandsinputted through manipulation panel 4, and the like. Thereby, secondcontroller 71 can form a print image on a surface of print medium 5.

Meanwhile, second image input unit loads image data of an image to beprinted from the outside in the same manner as first image input unit 52according to embodiment 1. Then, in the case of forming a print image ona surface of print medium 5 in the bordered printing mode, second imageinput unit 73 generates print image data of the print image having animage size slightly smaller than the size of the print medium for use inbordered printing as in the case of first image input unit 52 describedabove. Alternatively, in the case of forming a print image on a surfaceof print medium 5 in the borderless printing mode, second image inputunit 73 generates print image data of the print image having an imagesize slightly larger than the size of the print medium for use inborderless printing, for example. Note that, in the case where a printimage is formed on a surface of print medium 5 with the first imageformation method, for example, print image data generated by secondimage input unit 73 for use in borderless printing is assigned, asappropriate, such an image size (hereinafter, such a size is alsoreferred to as a first borderless image size) that an edge portion ofthe image extends beyond the top and bottom edges and the left and rightedges of the surface of print medium 5 by an equal width or differentwidths according to the amount of first misregistration. Alternatively,in the case where a print image is formed on a surface of print medium 5with the second image formation method, print image data generated bysecond image input unit 73 for use in borderless printing is assigned,as appropriate, such an image size (hereinafter, such a size is alsoreferred to as a second borderless image size) that an edge portion ofthe image extends beyond the top and bottom edges and the left and rightedges of the surface of print medium 5 by an equal width or differentwidths according to the amount of the second misregistration. Note,however, that, since there is tendency that a larger portion of theground color spreads out from under the upper color with the secondimage formation method than with the first image formation method asdescribed above, the second borderless image size is assigned so as tobe wider than the first borderless image size in at least one of themain-scanning direction and the sub-scanning direction.

Thus, in storage unit 72, second controller 71 stores theabove-mentioned first pixel search range information and second pixelsearch range information, and stores the above-mentioned first areadetection range information and second area detection range informationfor use in processing print image data for bordered printing. Inaddition, according to the amount of the first misregistration, thefirst borderless image size, and the size of the medium (medium size),color printer 70 assigns, as appropriate, a third area detection rangebeing in the shape of a frame going around a print image along the edgesof the image, being an area extending beyond print medium 5, and beingused to detect an edge-portion area to be corrected in an edge portionof the print image of the first borderless image size (hereinafter, suchan area is also referred to as an edge-portion correction area forborderless mode). Likewise, in an edge portion of a print image of thesecond borderless image size, color printer 70 assigns, as appropriate,a fourth area detection range, which is an area extending beyond printmedium 5 and is used to detect an edge-portion correction area for theborderless mode, according to the amount of the second misregistration,the second borderless image size, and the medium size. Note that thethird area detection range and the fourth area detection range are eachin the shape of a frame whose widths between left/right strip-shapedportions and between top/bottom strip-shaped portions are equal to, ordifferent from, each other as in the case of the first area detectionrange and the second area detection range, and they are assigned so thatthe fourth area detection range may be wider than the third areadetection range. Thus, in storage unit 72, second controller 71 storesthird area detection range information indicating the third areadetection range and fourth area detection range information indicatingthe fourth area detection range. Note that, in storage unit 72, secondcontroller 71 stores first borderless image size information indicatingthe first borderless image size represented with the number of pixels inthe main-scanning direction and in the sub-scanning direction, and alsostores second borderless image size information indicating the secondborderless image size represented with the number of pixels in themain-scanning direction and in the sub-scanning direction.

Storage unit 72 stores therein a second image processing program havinga configuration different from the first image processing programaccording to embodiment 1 described above. With the configuration above,upon receiving print image data from second image input unit 73 in theformation of a print image, second controller 71 executes second imageprocessing by using the first and second pixel search range and thefirst to fourth detection range as appropriate to prevent the groundcolor from spreading out from under the upper color throughout the printimage (i.e., in an edge portion and a central portion of the image).Thus, with FIG. 15, in which portions that are corresponding to those ofFIG. 3 are given reference numerals that are the same as those of FIG.3, print image data generation processing executed by second image inputunit 73 is described specifically below. Besides, while variousfunctions that second controller 71 implements according to the secondimage processing program are indicated by functional circuit blocks forthe sake of convenience, the second image processing that secondcontroller 71 executes according to the second image processing programis described specifically below as the processing executed by thefunctional circuit blocks.

In this case, in the same manner as setting unit 61 according toembodiment 1 described above, setting unit 76 of second spread-outcorrection unit 75 detects an image formation method and the type of theground color and the upper color. Then, setting unit 76 makes a settingsuch that all parts of second spread-out correction unit 75 (i.e.,boundary correction area detector 62, second edge-portion correctionarea detector 77, and second correction processor 78) execute processingaccording to the image formation method and the type of the ground colorand the upper color thus detected, and such that second image input unit73 generates print image data of a print image represented with theground color and the upper color thus detected. Further, at the time offorming a print image for example, setting unit 76 lets the user directa printing mode at this time (i.e., either of the bordered printing modeand the borderless printing mode) on a setting screen displayed onmanipulation panel 4. Then, if the formation of a print image in thebordered printing mode is directed by the user, setting unit 76 makes asetting such that second image input unit 73 generates print image datafor a bordered printing in addition to the above setting. On the otherhand, if the formation of a print image in the borderless printing modeis directed by the user, setting unit 76 retrieves first borderlessimage size information or second borderless image size information fromstorage unit 72 depending on which image formation method (i.e., thefirst image formation method and the second image formation method) isused at this time and sends it to second image input unit 73. At thesame time, setting unit 76 makes a setting such that second image inputunit 73 generates print image data for borderless printing in additionto the above setting. Incidentally, if image data of an image to beprinted is given to second image input unit 73 from an informationprocessing device connected to color printer 70, setting unit 76 maydirect that the information processing device direct a printing modebesides letting the user direct a printing mode on the setting screen.

Meanwhile, second image input unit 73 generates print image data forbordered printing or print image data for borderless printing accordingto the setting made by setting unit 76, and sends boundary correctionarea detector 62 the print image data and printing mode informationindicating whether the print image data is for bordered printing or forborderless printing irrespective of whichever print image data isgenerated. However, second image input unit 73 generates print imagedata for bordered printing in the same manner as first image input unit52 according to embodiment 1 described above. Thus, in the followingdescription, only the process of generating print image data forborderless printing is described as to the processing executed by secondimage input unit 73. In addition, upon receiving print image data andprinting mode information from second image input unit 73, boundarycorrection area detector 62 detects a boundary correction area based onthe print image data and sends a boundary correction area detection datato second edge-portion correction area detector 77 together with theprint image data and the printing mode information. However, boundarycorrection area detector 62 executes boundary correction area detectionprocessing as in the case of embodiment 1, described above, irrespectiveof which of print image data for bordered printing and print image datafor borderless printing boundary correction area detector 62 retrieves.Thus, a specific description on the processing of printing boundarycorrection area detector 62 is omitted. Further, upon retrieving printimage data and printing mode information, together with boundarycorrection area detection data from boundary correction area detector62, second edge-portion correction area detector 77 judges a printingmode based on the printing mode information. Then, second edge-portioncorrection area detector 77 executes the same processing as the firstedge-portion correction area detection processing executed by firstedge-portion correction area detector 63 if the judged printing mode isthe bordered printing mode, but executes a processing different from thefirst edge-portion correction area detection processing if the judgedprinting mode is the borderless printing mode. Thus, in the followingdescription, as to the processing executed by second edge-portioncorrection area detector 77, the processing executed when the judgedprinting mode is the bordered printing mode is not described, and onlythe processing executed when the judged printing mode is the borderlessprinting mode is described. Furthermore, second correction processor 78executes the same processing irrespective of whether the printing modeis the bordered printing mode or the borderless printing mode. Thus, inthe following description, as to the processing executed by secondcorrection processor 78, only the processing executed when the printingmode is the borderless printing mode is described, and the processingexecuted when the printing mode is the bordered printing mode is notdescribed.

In the case where a print image in which white serves as the groundcolor is formed on a surface of a plain paper sheet in the borderlessprinting mode, upon loading image data of an image to be printed fromthe outside, second image input unit 73 generates print image data ofthe print image having the first borderless image size and representedwith the colors of cyan, magenta, yellow, black, and white based on theloaded image data. In this event, for example, for a portion of theprint image which entirely overlaps the surface of print medium 5,second image input unit 73 stores, in the print image data for everypixel of that portion, five kinds of pixel values represented bynormalizing the densities of cyan, magenta, yellow, black, and whiteinto values from “0” to “255” respectively based on the pattern of theprint image, in the same manner as first image input unit 52 accordingto embodiment 1 described above. On the other hand, for an area of theprint image which extends beyond the print medium, second image inputunit 73 stores, in the print image data for every pixel of that area,five kinds of pixel values of “0” indicating that none of the colors ofcyan, magenta, yellow, black, and white is used for representing thepixel, for example. Second image input unit 73 sends the print imagedata generated in this manner to boundary correction area detector 62together with the printing mode information indicating the borderlessprinting mode applied at this time. Then, upon receiving the boundarycorrection area detection data together with the print image data andthe printing mode information from boundary correction area detector 62,second edge-portion correction area detector 77 executes secondedge-portion correction area detection processing and judges a printingmode applied at this time (i.e., the borderless printing mode in thiscase). In addition, second edge-portion correction area detector 77retrieves first pixel search range information and third area detectionrange information from storage unit 72 according to the setting made bysetting unit 76 as well as the judgment result. In this event, asillustrated in FIG. 16, while shifting first pixel search range SE1indicated by the first pixel search range information in themain-scanning direction or in the sub-scanning direction sequentially ona pixel-by-pixel basis on print image IM2 which is based on the printimage data, second edge-portion correction area detector 77 makes everypixel in print image IM1 positioned at the center of first pixel searchrange SE1 sequentially one at a time to designate the pixel as focusedpixel P51. In addition, every time second edge-portion correction areadetector 77 designates each pixel as a focused pixel PS1 on print imageIM1 one at a time, it judges whether or not both conditions wherefocused pixel PS1 is a pixel of extension area AR5 and where at leastone of neighboring pixels PN1 is a pixel of colored area AR2 aresatisfied on the basis of a third area detection range (not illustrated)indicated by the third area detection range information and havingwidths between left/right strip-shaped portions and between top/bottomstrip-shaped portions that are equal to each other, for example, andfive kinds of pixel values of each of neighboring pixels PN1 in firstpixel search range SE1. Note that second edge-portion correction areadetector 77 may judge that focused pixel PS1 is a pixel of extensionarea AR5 being the third area detection range if the coordinates offocused pixel PS1 satisfy at least one of four kinds of conditionsrepresented with the following formulae (5) to (8):

x<W2−  (5);

y<W2  (6);

x≧X2−W2  (7); and

y≧Y2−W2  (8),

where: X2 and Y2 indicate the horizontal size and the vertical sizerepresented with the number of pixels in the main-scanning direction andin the sub-scanning direction, respectively, with the left upper cornerof print image IM2 used as the point of origin. W2 indicates the widthof each of image left/right edge portions and image top/bottom edgeportions of extension area AR5 represented with the number of pixelsthereof; and (x, y) indicates the coordinates of focused pixel PS1.Then, if a focused pixel is a pixel of extension area AR5 and at leastone of neighboring pixels PN1 is a pixel of colored area AR2, secondedge-portion correction area detector 77 judges that this focused pixelPS1 is an edge-portion correction pixel. In contrast, if focused pixelPS1 is a pixel outside extension area AR5, second edge-portioncorrection area detector 77 judges that this focused pixel PS1 is anon-correction pixel irrespective of whether or not any of neighboringpixels PN1 is a pixel of colored area AR2. Further, if focused pixel PS1is a pixel of extension area AR5 but all of neighboring pixels PN1 arepixels in colorless area AR1, second edge-portion correction areadetector 77 also judges that this focused pixel PS1 is a non-correctionpixel. In this manner, based on the judgment result, second edge-portioncorrection area detector 77 detects an edge-portion correction area forthe borderless mode, which is formed of edge-portion correction pixelsand adjacent to colored area AR2 on the central side of the image, inextension area AR5 of print image IM2. Note that second edge-portioncorrection area detector 77 generates edge-portion correction areadetection data indicating the edge-portion correction area for theborderless mode while judging, one at a time, whether each of the pixelsin print image IM2 is an edge-portion correction pixel or anon-correction pixel. Specifically, second edge-portion correction areadetector 77 stores data in the edge-portion correction area detectiondata such that it associates a value of “2” indicating an edge-portioncorrection pixel with a pixel in print image IM2 if judging that thepixel is an edge-portion correction pixel, and such that it associates avalue of “0” indicating a non-correction pixel with a pixel in printimage IM2 if judging that the pixel is a non-correction pixel. Note thatsecond edge-portion correction area detector 77 stores a value of “2,”indicating an edge-portion correction pixel of an edge-portioncorrection area for the borderless mode, in the edge-portion correctionarea detection data if detecting the edge-portion correction area forthe borderless mode in print image IM2 for borderless printing in theabove manner, but stores a value of “1,” indicating an edge-portioncorrection pixel of an edge-portion correction area for bordered mode,in the edge-portion correction area detection data if detecting theedge-portion correction area for bordered mode in the print image forbordered printing. Second edge-portion correction area detector 77thereby makes the edge-portion correction area detection datarecognizable as to which of the edge-portion correction area for thebordered mode and the edge-portion correction area for the borderlessmode the edge-portion correction area detection data indicates. Then,upon detecting the edge-portion correction area for the borderless modein this manner, second edge-portion correction area detector 77 sendsthe edge-portion correction area detection data to second correctionprocessor 78 together with the print image data and the boundarycorrection area detection data.

Upon receiving the boundary correction area detection data and theedge-portion correction area detection data, together with the printimage data from second edge-portion correction area detector 77, secondcorrection processor 78 retrieves first pixel search range informationfrom storage unit 72 and executes second correction processing accordingto the setting made by setting unit 76. In this event, while shiftingfirst pixel search range SE1 (not illustrated in FIG. 7) indicated bythe first pixel search range information in the main-scanning directionor in the sub-scanning direction sequentially on a pixel-by-pixel basison print image IM2 which is based on the print image data, secondcorrection processor 78 designates every pixel in print image IM2 as afocused pixel PS1 at the center of first pixel search range SE1sequentially one at a time, for example. In addition, every time secondcorrection processor 78 designates each pixel as a focused pixel PS1 onprint image IM2 one at a time, it judges whether or not focused pixelPS1 is an edge-portion correction pixel of the edge-portion correctionarea for the borderless mode, whether or not the focused pixel is anedge-portion correction pixel of the edge-portion correction area forthe bordered mode, and whether or not the focused pixel is a boundarycorrection pixel of the boundary correction area. As a result of thejudgment, if focused pixel PS1 is an edge-portion correction pixel ofthe edge-portion correction area for the borderless mode, secondcorrection processor 78 changes the pixel value of white that thisfocused pixel PS1 (i.e., boundary correction pixel) has from itsoriginal value of “0” to the largest value among the pixel values ofwhite that neighboring pixels PN1 in first pixel search range SE1respectively have. In the same way, second correction processor 78changes each of the pixel values of cyan, magenta, yellow, and blackthat this focused pixel PS1 (i.e., boundary correction pixel) has fromits original value of “0” to the largest value among the pixel values ofthe corresponding color that neighboring pixels PN1 in first pixelsearch range SE1 respectively have. Note that, if focused pixel PS1 is aboundary correction pixel, second correction processor 78 changes thepixel values of cyan, magenta, yellow, and black except for the pixelvalue of white among the five kinds of pixel values of this focusedpixel PS1 (i.e., boundary correction pixel) in the same manner as firstcorrection processor 64 according to embodiment 1 described above. Onthe other hand, if focused pixel PS1 is a non-correction pixel (that is,focused pixel PS1 is neither an edge-portion correction pixel nor aboundary correction pixel), second correction processor 78 leaves thefive kinds of pixel values of this focused pixel PS1 unchanged.Incidentally, second correction processor 78 corrects an edge-portioncorrection pixel in the above manner when receiving print image data forborderless printing from second edge-portion correction area detector77, but processes an edge-portion correction pixel in the same manner asfirst correction processor 64 according to embodiment 1 described abovewhen receiving print image data for bordered printing from secondedge-portion correction area detector 77. In this manner, secondcorrection processor 78 corrects print image IM2 for borderless printingso that the edge-portion correction area for the borderless modeextending along the edges of the image may be represented with theground color and the upper color laid one over another, and thus widensthe width of colored area AR2 in the edge portion of the image such thatcolored area AR2 expands toward the edges of the image from an areahaving the medium size in the image. Then, second correction processor78 sends the print image data of print image IM2 thus corrected tooutput image processor 65 as corrected print image data.

Thereby, color printer 70 can form print image IM2, whose edge-portioncorrection area for the borderless mode and boundary correction area arecorrected, in the borderless printing mode on the entire surface ofprint medium 5 on the basis of the corrected print image data. Notethat, in this event, an edge portion of a toner image is leftun-transferred on the surface of transfer belt 33 when transfer unit 15transfers the toner image onto the surface of print medium 5 from thesurface of transfer belt 33 in color printer 70 because the firstborderless image size of print image IM2 based on the corrected printimage data is larger than the medium size. However, such residual tonercan be removed with cleaning blade 40. Meanwhile, when forming a printimage on a surface of print medium 5 in the borderless printing mode, aconventional color printer generates print image data of the print imagehaving an image size equal to the medium size. Thus, as illustrated inFIG. 17A, as long as the conventional color printer can form a printimage on a surface of print medium 5 such as a plain paper sheet withoutany misalignment of the print image itself relative to the surface, forexample, it is possible to lay ground color GC3 and upper color UC3 ofthe same width one over another in a colored area in an edge portion ofthe image while aligning them along an edge of the sheet. However, asillustrated in FIG. 17B, because the conventional color printer does notperform the second image processing as in embodiment 2 on print imagedata at all, ground color GC3 spreads out from under upper color UC3 ifground color GC3 and upper color UC3 laid one over another aremisaligned with each other in the colored area in the edge portion ofthe image, which deteriorates the quality of the print image. Further,as illustrated in FIG. 17C, if the print image itself is misalignedrelative to the surface of print medium 5 in the conventional colorprinter, ground color GC3 and upper color UC3 are moved away from theedge of the sheet and the color of the sheet (i.e., the color of printmedium 5) turns visible in addition to the upper color, which stilldeteriorates the quality of the print image. On the other hand, colorprinter 70 according to embodiment 2 generates print image data of printimage IM2 of the first borderless image size larger than the mediumsize, and corrects an edge-portion correction area for the borderlessmode, extending along the edges of the image, in print image IM2 basedon the print image data to widen the width of colored area AR2 in anedge portion of the image such that colored area AR2 expands toward theedges of the image from an area having the medium size in the image.Thus, as illustrated in FIG. 18A, when color printer 70 forms printimage IM2 on a surface of print medium 5 such as a plain paper sheet,for example, and if there is no misalignment of the print image itselfrelative to the surface, it is possible to make a part of ground colorGC4 and upper color UC4 laid one over another spread out beyond the edgeof the sheet in the edge portion of the image, and thereby to preventground color GC4 and the color of the sheet from becoming visible.Further, as illustrated in FIG. 18B, even if ground color GC4 and uppercolor UC4 laid one over another are misaligned with each other in theedge portion of the image in color printer 70, it is possible to makeground color GC4 spread out from under upper color UC4 outside the edgeof the sheet, and thereby to prevent ground color GC spreading out fromunder upper color UC4 from becoming visible. Furthermore, as illustratedin FIG. 18C, even if print image IM2 itself is misaligned relative tothe surface of print medium 5 in color printer 70, it is possible tomake ground color GC4 and upper color UC4 laid one over another alignedalong the edge of the sheet in the edge portion of the image, andthereby to prevent ground color GC4 and the color of the sheet frombecoming visible in this case as well.

Next, in the case where print image IM2 in which white as the specialcolor serves as the ground color is formed in the borderless printingmode on the surface of a transfer paper sheet, upon loading image dataof an image to be printed from the outside, second image input unit 73generates print image data similar to the above case except that thesize of the print image (the second borderless image size in this case)as well as the width of an extension area of the image are different,and sends it to boundary correction area detector 62 together withprinting mode information. Then, upon receiving boundary correction areadetection data as well as the print image data and the printing modeinformation from boundary correction area detector 62, secondedge-portion correction area detector 77 executes second edge-portioncorrection area detection processing and judges a printing mode (i.e.,the borderless printing mode in this case) based on the printing modeinformation. Further, second edge-portion correction area detector 77retrieves the second pixel search range information and the fourth areadetection range information from storage unit 72 in this case accordingto the setting made by setting unit 76 as well as the judgment result,but executes the second edge-portion correction area detectionprocessing similar to the above to detect an edge-portion correctionarea for the borderless mode. Second edge-portion correction areadetector 77 then sends edge-portion correction area detection data tosecond correction processor 78 together with the print image data andthe boundary correction area detection data. Upon receiving the boundarycorrection area detection data and the edge-portion correction areadetection data as well as the print image data from second edge-portioncorrection area detector 77, second correction processor 78 retrievesthe second pixel search range information from storage unit 72 accordingto the setting made by setting unit 76, but executes the secondcorrection processing similar to the above to generate corrected printimage data and sends it to output image processor 65.

Next, in the case where print image in which the base colors serve asthe ground color (that is, the color of clear as the special colorserves as the upper color) is formed in the borderless printing mode onthe surface of a plain paper sheet, upon loading image data of an imageto be printed from the outside, second image input unit 73 generatesprint image data similar to the above case except that the pixel valueof clear instead of the pixel value of white is stored in each pixel,and sends it to boundary correction area detector 62 together withprinting mode information. Then, upon receiving boundary correction areadetection data as well as the print image data and the printing modeinformation from boundary correction area detector 62, secondedge-portion correction area detector 77 executes a second edge-portioncorrection area detection processing and judges a printing mode (i.e.,the borderless printing mode in this case) based on the printing modeinformation. Further, second edge-portion correction area detector 77retrieves the second pixel search range information and the fourth areadetection range information from storage unit 72 according to thesetting made by setting unit 76 as well as the judgment result, andexecutes the second edge-portion correction area detection processingsimilar to the above to detect an edge-portion correction area for theborderless mode. Second edge-portion correction area detector 77 thensends edge-portion correction area detection data to second correctionprocessor 78 together with the print image data and the boundarycorrection area detection data. Upon receiving the boundary correctionarea detection data, the edge-portion correction area detection data andthe print image data from second edge-portion correction area detector77, second correction processor 78 retrieves the second pixel searchrange information from storage unit 72 according to the setting made bysetting unit 76, and executes the second correction processing similarto the above to generate corrected print image data and sends it tooutput image processor 65.

(2-3) Second Image Processing

Next, with the flowcharts illustrated in FIGS. 19 and 20 in whichportions that are correspond to those of FIGS. 12 and 13 are givenreference numerals that are the same as those of FIGS. 12 and 13, adescription is given of second edge-portion correction area detectionprocessing procedure RT4 and second correction processing procedure RT5that second controller 71 executes as part of a second image processingprocedure according to the second image processing program. Note thatboundary correction area detection processing procedure RT1, that secondcontroller 71 executes as part of the second image processing procedure,is similar to that in the case of embodiment 1, and therefore is notdescribed. When first controller 50 finishes boundary correction areadetection processing procedure RT1, it subsequently starts secondedge-portion correction area detection processing procedure RT4illustrated in FIG. 19 according to the second image processing program.Upon starting second edge-portion correction area detection processingprocedure RT4, in step SP31, second controller 71 judges whether or notthe printing mode at this time is the borderless printing mode, andproceeds to step SP32 if a positive result is obtained. Then, in stepSP32, second controller 71 designates one of the pixels in a print imageas a focused pixel PS1, and judges whether or not both conditions aresatisfied as to where this focused pixel PS1 is a pixel of extensionarea AR5, and where any pixel of colored area AR2 exists within a pixelsearch range (i.e., among neighboring pixels PN1 in first pixel searchrange SE1 or the second pixel search range which are located aroundfocused pixel PS1). If a positive result is obtained in step SP 32, itindicates that focused pixel PS1 is located near colored area AR2 in anedge portion of the image and therefore the width of colored area AR2can be widened toward the edges of the image (i.e., toward the outsideof print medium 5) by correcting the pixel values of focused pixel PS1so that the focused pixel may be represented with the ground color andthe upper color. Thus, if a positive result is obtained in step SP32,second controller 71 proceeds to step SP33 to judge that this focusedpixel PS1 is an edge-portion correction pixel of the edge-portioncorrection area for the borderless mode, and proceeds to next step SP34.In contrast, if a negative result is obtained in step SP32, it indicatesthat focused pixel PS1 is relatively away from colored area AR2 in theedge portion of the image, and therefore the width of colored area AR2cannot be widened toward the edges of the image even by correcting thepixel values of focused pixel PS1 so that the focused pixel may berepresented with the ground color and the upper color. Thus, if anegative result is obtained in step SP32, second controller 71 proceedsto step SP35 to judge that this focused pixel PS1 is a non-correctionpixel outside the edge-portion correction area for the borderless mode,and proceeds to step SP34. Note that, if a negative result is obtainedin step SP31 because the printing mode at this time is the borderedprinting mode, second controller 71 proceeds to step SP11 and executesthe processing in step SP11, then executes the processing in step SP12or the processing in step SP14, and then proceeds to step SP34. In stepSP34, second controller 71 judges whether or not the judgment on all thepixels in the print image is over, and goes back to step SP31 if anegative result is obtained. When second controller 71 finishes judgingall the pixels in the print image to be either an edge-portioncorrection pixel or a non-correction pixel, it detects the edge-portioncorrection area for the borderless mode or edge-portion correction areafor bordered mode AR3 based on the judgment result. Then, if a positiveresult is obtained in step SP34, second controller 71 proceeds to nextstep SP36 to terminate second edge-portion correction area detectionprocessing procedure RT4.

When second controller 71 finishes second edge-portion correction areadetection processing procedure RT4, it subsequently starts secondcorrection processing procedure RT5 illustrated in FIG. 20 according tothe second image processing program. Upon starting second correctionprocessing procedure RT5, in step SP41, second controller 71 designatesone of the pixels in the print image as a focused pixel PS1, and judgeswhether or not this focused pixel PS1 is an edge-portion correctionpixel of the edge-portion correction area for the borderless mode. If apositive result is obtained, second controller 71 proceeds to step SP42.Then, in step SP42, second controller 71 corrects the edge-portioncorrection area for the borderless mode so that all of the five kinds ofpixel values of the edge-portion correction pixel of the edge-portioncorrection area for the borderless mode may be replaced with a valuelarger than “0,” and proceeds to next step SP43. In contrast, if anegative result is obtained in step SP41, second controller 71 proceedsto step SP44 to judge whether or not focused pixel PS1 is anedge-portion correction pixel of the edge-portion correction area forthe bordered mode. If a positive result is obtained in step SP44, secondcontroller 71 executes the processing in step SP22 and then proceeds tostep SP43. Alternatively, if a negative result is obtained in step SP44,second controller 71 executes the processing in step SP24, and thenexecutes the processing in step SP25 and proceeds to step SP43 orproceeds to step SP43 without executing the processing in step SP25. Instep SP43, second controller 71 judges whether or not the correction isover on the edge-portion correction area for borderless mode andboundary correction area AR4 in the print image or the correction onedge-portion correction area for bordered mode AR3 and boundarycorrection area AR4 in the print image. If a negative result is obtainedin step SP43 because there is a pixel not yet judged to be anedge-portion correction pixel or not nor judged to be a boundarycorrection pixel or not and therefore the correction is not over, secondcontroller 71 goes back to step SP41. Then, if a positive result isobtained in step SP43 because the correction on the edge-portioncorrection area for the borderless mode and boundary correction area AR4in the print image or the correction on the edge-portion correction areafor bordered mode AR3 and boundary correction area AR4 in the printimage is over, second controller 71 proceeds to next step SP45 toterminate second correction processing procedure RT5.

(2-4) Operation and Effect of Embodiment 2

When color printer 70 having the above configuration forms print imageIM2 in the borderless printing mode, second image input unit 73generates print image data of print image IM2 which has an image sizelarger than the medium size and in which colorless extension area AR5extends beyond an area having the medium size in the image. Then, incolor printer 70, second controller 71 generates corrected print imagedata by detecting the edge-portion correction area for the borderlessmode, which extends along the edges of the image adjacent to coloredarea AR2, in extension area AR5 of print image IM2 which is based on theprint image data, and then making such a correction that the detectedarea may be represented with the ground color and the upper color laidone over another.

With the configuration above, color printer 70 can widen the width ofcolored area AR2 in print image IM2 based on the print image data suchthat colored area AR2 expands toward the edges of the image from an areahaving the medium size in the image. Accordingly, even if print imageIM2 itself is misaligned relative to the surface of print medium 5 orthe upper color and the ground color laid one over another in the edgeportion of print image IM2 are misaligned with each other when colorprinter 70 forms print image IM2 on a surface of print medium 5 in theborderless printing mode, it is possible to avoid a situation where thecolor of print medium 5, which should be originally hidden under printimage IM2 and invisible, turns visible or where the ground colorspreading out from under the upper color is visible. Because it ispossible to avoid this type situation, it is thus possible to preventthe deterioration in the quality of print image IM2.

In addition, in color printer 70, second controller 71 corrects theedge-portion correction area for the borderless mode such that, for eachpixel of the edge-portion correction area for borderless mode, each ofthe pixel values of the pixel is replaced with the largest value amongthe corresponding pixel values of one or more pixels of colored area AR2in the pixel search range, including the pixel as a center pixel.Accordingly, color printer 70 can expand a portion of colored area AR2,being a boundary with the edge-portion correction area for theborderless mode, toward the edge-portion correction area for theborderless mode while hardly changing the color thereof. Thus, colorprinter 1 can also prevent a deterioration in the image quality whichwould otherwise be caused if the portion of colored area AR2 expanded bythe correction on the edge-portion correction area for the borderlessmode turns to a color different from its original color.

(3) Other Embodiments (3-1) Other Embodiment 1

Note that, in embodiments 1 and 2 described above, the description isgiven of the case where an edge-portion correction area for theborderless mode is corrected such that each of the pixel values of theground color and the upper color that each pixel of the edge-portioncorrection area for borderless mode has is replaced with the largestvalue among the pixel values of the corresponding one of the groundcolor and the upper color that pixels in a pixel search range includingthe pixel as a center pixel respectively have. However, not limitedthereto, the invention may be so configured that the edge-portioncorrection area for the borderless mode is corrected such that each ofthe pixel values of the ground color and the upper color that each pixelof the edge-portion correction area for borderless mode has is replacedwith the average value of the pixel values of the corresponding one ofthe ground color and the upper color that pixels in a pixel search rangeincluding the pixel as a center pixel respectively have. With the aboveconfiguration as well, the invention can expand a portion of coloredarea AR2 on a central side of the image, being a boundary with theedge-portion correction area for the borderless mode, toward theedge-portion correction area for the borderless mode while hardlychanging the color thereof. Alternatively, the invention may be soconfigured that the edge-portion correction area for borderless mode iscorrected to be represented only with the upper color such that only thepixel value of the upper color that each pixel of the edge-portioncorrection area for borderless mode has is replaced with the largestvalue among the pixel values of the upper color that pixels in a pixelsearch range including the pixel as a center pixel respectively have, orreplaced with the average value of the pixel values of the upper colorthat pixels in the pixel search range including the pixel as a centerpixel respectively have. With the above configuration as well, theinvention can achieve an effect similar to that in embodiment 2described above.

(3-2) Other Embodiment 2

Further, in embodiments 1 and 2 described above, the description isgiven of the case where an edge-portion correction area for the borderedmode is corrected such that the pixel value of the ground color thateach pixel of the edge-portion correction area for bordered mode has isreplaced with “0.” However, not limited thereto, the invention may be soconfigured that the edge-portion correction area for the bordered modeis corrected such that the pixel value of the ground color that eachpixel of the edge-portion correction area for the bordered mode has isreplaced with the average value of the pixel values of the ground colorthat pixels in a pixel search range including the pixel as a centerpixel respectively have, or is replaced with a predetermined value whichis selected within a range that a pixel value can take (i.e., from “0”to “255”) excluding the smallest value and the largest value. With theabove configuration, the invention can prevent a situation where, whenthe width of colored area AR2 including the edge-portion correction areafor the bordered mode is relatively narrow in an edge portion of animage, for example, the width of the ground color in colored area AR2 isfurther narrowed and the ground color becomes unable to fully exert itsfoundation function, which would otherwise be caused if the pixel valueof the ground color that each pixel of the edge-portion correction areafor bordered mode has is replaced with “0.” Besides, in the case wherethe pixel value of the ground color that each pixel of an edge-portioncorrection area for the bordered mode has, is replaced with the averagevalue of the pixel values of the ground color that pixels in a pixelsearch range including the pixel as a center pixel respectively have,the invention may set the pixel search range wider than the width of theedge-portion correction area for bordered mode. By doing so, whencolorless area AR1 abuts on the edge-portion correction area for thebordered mode, for example, the pixel value of the ground color thateach pixel of the edge-portion correction area for the bordered modehas, can be made smaller than the largest value within a range that thisvalue can take. As a result, although the ground color spreads out fromunder the upper color if the ground color and the upper color laid oneover another are misaligned with each other in an edge portion of aprint image when the image is formed on a surface of print medium 5, theinvention can make the density of the spread-out portion relatively lowto make this portion less likely to stand out, so that the deteriorationin the quality of the print image can be reduced. In addition, in thecase where the pixel value of the ground color that each pixel of theedge-portion correction area for the bordered mode has is replaced witha predetermined value which is selected within a range that a pixelvalue can take excluding the smallest value and the largest value, evenif the predetermined value is set as small as possible, the inventioncan make the ground color, which spreads out from under the upper colorwhen a print image is formed on a surface of print medium 5, less likelyto stand out and thus can reduce the deterioration in the quality of theprint image.

(3-3) Other Embodiment 3

Further, in embodiments 1 and 2 described above, the description isgiven of the case where a boundary correction area adjacent to coloredarea AR2 is detected in colorless area AR1 located in a central portionof a print image and corrected such that the pixel value of the uppercolor that each pixel of the boundary correction area has is replacedwith the largest value among the pixel values of the upper color thatpixels in a pixel search range including the pixel as a center pixelrespectively have. However, not limited thereto, the invention may be soconfigured that a boundary correction area adjacent to colored area AR2is detected in colorless area AR1 located in a central portion of aprint image and corrected such that the pixel value of the upper colorthat each pixel of the boundary correction area has is replaced with theaverage value of the pixel values of the upper color that pixels in apixel search range including the pixel as a center pixel respectivelyhave. With the above configuration as well, the invention can expand aportion of colored area AR2 in a central portion of the image, being aboundary with the boundary correction area, toward the boundarycorrection area while hardly changing the color thereof. Alternatively,the invention may be so configured that a boundary correction areaadjacent to colorless area AR1 is detected in colored area AR2 locatedin the central portion of the print image and corrected such that thepixel value of the ground color that each pixel of the boundarycorrection area has is replaced with “0.” With the above configurationas well, the invention can narrow the width of the ground color incolored area AR2 relative to the width of the upper color laid over theground color, and accordingly this makes it possible to avoid thesituation where the ground color spreads out from under the upper colorof colored area AR2 in the central portion of print image IM1 when theimage is formed on a surface of print medium 5. Still alternatively, theinvention may be so configured that, when a boundary correction area isdetected in colored area AR2 located in the central portion of the printimage, the boundary correction area is corrected such that the pixelvalue of the ground color that each pixel of the boundary correctionarea has is replaced with the average value of the pixel values of theupper color that pixels in a pixel search range including the pixel as acenter pixel respectively have. With the above configuration, theinvention can prevent a situation where, when the width of colored areaAR2 is relatively narrow, for example, the width of the ground color isfurther narrowed and the ground color becomes unable to fully exert itsfoundation function, which would otherwise be caused if the pixel valueof the ground color is replaced with “0.”

(3-4) Other Embodiment 4

Further, in embodiments 1 and 2 described above, the description isgiven of the case where an edge-portion correction area for the borderedmode, or an edge-portion correction area for the borderless mode, isdetected in a print image after a boundary correction area is detected.However, not limited thereto, the invention may be so configured thatthe boundary correction area is detected in the print image after theedge-portion correction area for the bordered mode or the edge-portioncorrection area for the borderless mode is detected, or may be soconfigured that the boundary correction area as well as the edge-portioncorrection area for the bordered mode or the edge-portion correctionarea for the borderless mode are detected in a time-sharing processingor at the same time.

(3-5) Other Embodiment 5

Further, in embodiments 1 and 2 described above, the description isgiven of the case where, while sequentially designating each of pixelsin a print image as a focused pixel, first controller 50 or secondcontroller 71 judges whether this focused pixel is an edge-portioncorrection pixel or a non-correction pixel to detect an edge-portioncorrection area for the borderless mode or an edge-portion correctionarea for the bordered mode. However, not limited thereto, the inventionmay be so configured as follows, for example. Specifically, first imageinput unit 52 or second image input unit 73 divides print image datainto data segments on several-lines by several-lines basis, furtherdivides each of the data segments into block data segments, and sendseach of the block data segments to first controller 50 or secondcontroller 71 together with information on the position of the blockdata segment in the print image data. Then, according to the positioninformation loaded together with the block data segments, firstcontroller 50 or second controller 71 detects an edge-portion correctionarea for the borderless mode or an edge-portion correction area for thebordered mode on a block-by-block basis while selectively using theblock data segments along the edges of the image. With the aboveconfiguration, the invention can reduce the processing of the loadplaced when first controller 50 or second controller 71 executes thefirst edge-portion correction area detection processing or the secondedge-portion correction area detection processing.

(3-6) Other Embodiment 6

Further, in embodiments 1 and 2 described above, the description isgiven of the case where first controller 50 and second controller 71execute the first and second image processing procedures, describedabove with FIGS. 11 to 13 and FIGS. 19 and 20, according to the firstand second image processing programs stored in storage units 51 and 72in advance. However, not limited thereto, the invention may be soconfigured that first controller 50 and second controller 71 of colorprinters 1 and 70 execute the first and second image processingprocedures with the first and second image processing programs installedvia a computer-readable storage medium storing therein the first andsecond image processing programs, or with the first and second imageprocessing programs installed from the outside using a wired/wirelesscommunication medium such as a local area network, the Internet, or adigital satellite broadcast. Incidentally, a computer-readable storagemedium through which to install the first and second image processingprograms in color printers 1 and 70 to make them executable may beimplemented by a package medium such as a flexible disc, a CD-ROM(Compact Disc-Read Only Memory), or a DVD (Digital Versatile Disc), ormay be implemented by a semiconductor memory, a magnetic disc, or thelike storing therein various programs temporarily or permanently.Further, a wired/wireless communication medium such as a local areanetwork, the Internet, or a digital satellite broadcast may be used as aunit that stores the first and second image processing programs in acomputer-readable storage medium. Furthermore, the first and secondimage processing programs may be stored in a computer-readable storagemedium via various communication interfaces such as a router and amodem.

(3-7) Other Embodiment 7

Further, in embodiments 1 and 2 described above, the description isgiven of the case where the image processing device according to theinvention is applied to color printers 1 and 70 of secondary transfertype described above with FIGS. 1 to 20. However, not limited thereto,the invention is widely applicable to other image processing devices ofvarious configurations including a color printer of primary transfertype, an MFP (Multi-Function Peripheral), a facsimile machine, amultifunction device, a copier, and an information processing devicesuch as a computer.

(3-8) Other Embodiment 8

Further, in embodiments 1 and 2 described above, the description isgiven of the case where each of first controller 50 and secondcontroller 71 described above with FIGS. 1 to 20 is employed as anedge-portion correction area detector that detects an edge-portioncorrection area in an edge portion of a print image based on print imagedata, the edge-portion correction area extending along the edges of theimage represented with the ground color and the upper color laid oneover another. However, not limited thereto, the invention may widelyemploy other edge-portion correction area detectors having variousconfigurations including an edge-portion correction area detectioncircuit having a hardware configuration for detecting an edge-portioncorrection area in an edge portion of a print image based on print imagedata, the edge-portion correction area extending along the edges of theimage represented with the ground color and the upper color laid oneover another.

(3-9) Other Embodiment 9

Further, in embodiments 1 and 2 described above, the description isgiven of the case where print image data of a print image describedabove with FIGS. 1 to 20 having an image size smaller than the mediumsize is employed as print image data of a print image in an edge portionof which an edge-portion correction area that extends along the edges ofthe image represented with the ground color and the upper color laid oneover another is detected. However, not limited thereto, the inventionmay widely employ other various kinds of print image data having variousconfigurations including print image data of a print image having thesame image size as the medium size and print image data that stores foreach pixel various pixel values, with which whether the pixel is to berepresented with the ground color and/or the upper color or not can beset, in place of, or in addition to, pixel values representing thedensities.

(3-10) Other Embodiment 10

Further, in embodiments 1 and 2 described above, the description isgiven of the case where each of first controller 50 and secondcontroller 71 described with FIGS. 1 to 20 is employed as a correctionprocessor that corrects an edge-portion correction area of a printimage. However, not limited thereto, the invention may widely employother correction processors having various configurations including acorrection processing circuit having a hardware configuration forcorrecting an edge-portion correction area of a print image.

The invention may be used for image processing devices including anelectrophotographic color printer, an MFP, a facsimile machine, amultifunction device, a copier, and an information processing device.

The invention includes other embodiments in addition to theabove-described embodiments without departing from the spirit of theinvention. The embodiments are to be considered in all respects asillustrative, and not restrictive. The scope of the invention isindicated by the appended claims rather than by the foregoingdescription. Hence, all configurations including the meaning and rangewithin equivalent arrangements of the claims are intended to be embracedin the invention.

1. An image processing device comprising a correction processorconfigured to correct an print image data by correcting pixels of anedge-portion correction area in an edge portion of a print image basedon the print image data, the edge-portion correction area extendingalong image edge that has a ground color and an upper color over theground color in the edge portion.
 2. The image processing deviceaccording to claim 1, wherein the correction processor is configured tocorrect the edge-portion correction area of the print image such thatthe edge-portion correction area has only the upper color without theground color.
 3. The image processing device according to claim 1,wherein the print image data includes, for each pixel, a ground-colorpixel value representing a first density of the ground color and anupper-color pixel value representing a second density of the uppercolor, and the correction processor is configured to correct theedge-portion correction area such that the edge-portion correction areahas only the upper color without the ground color, by replacing theground-color pixel value of each pixel of the edge-portion correctionarea in the print image with “0.”
 4. The image processing deviceaccording to claim 1, wherein the print image data includes, for eachpixel, a ground-color pixel value representing a first density of theground color and an upper-color pixel value representing a seconddensity of the upper color, and the correction processor is configuredto correct the edge-portion correction area such that the ground-colorpixel value of each pixel of the edge-portion correction area in theprint image is replaced with an average value of the ground-color pixelvalues of pixels in a pixel search range including the pixel as a centerpixel.
 5. The image processing device according to claim 1, furthercomprising an edge-portion correction area detector configured to detectthe edge-portion correction area in the edge portion of the print imagebased on the print image data, the edge-portion correction areaextending along the image edge that has the ground color and the uppercolor over the ground color in the edge portion, wherein
 6. The imageprocessing device according to claim 5, wherein the edge-portioncorrection area detector configured to detect the edge-portioncorrection area along the image edge within an area detection range inthe image edge portion of the print image based on the print image data,the area detection range having a width set according to an amount ofmisregistration estimated to occur between the ground color and theupper color laid one over another when the print image is formed on aprint medium.
 7. The image processing device according to claims,wherein, when the print image is formed with a first image formationmethod, the edge-portion correction area detector detects theedge-portion correction area along the image edge within a first areadetection range in the edge portion of the print image based on theprint image data, the first area detection range having a width setaccording to an amount of first misregistration estimated to occurbetween the ground color and the upper color laid one over another whenthe print image is formed on a surface of a print medium with the firstimage formation method, and, when the print image is formed with asecond image formation method, the edge-portion correction area detectordetects the edge-portion correction area along the image edge within asecond area detection range in the edge portion of the print image basedon the print image data, the second area detection range having a widthset according to an amount of second misregistration, different from theamount of first misregistration, estimated to occur between the groundcolor and the upper color laid one over another when the print image isformed on the surface of the print medium with the second imageformation method.
 8. The image processing device according to claim 1,wherein the print image data is a bordered print image data of abordered print image having an image size smaller than a medium size. 9.The image processing device according to claim 8, further comprising anedge-portion correction area detector configured to detect theedge-portion correction area in the edge portion of the print imagebased on the print image data, the edge-portion correction areaextending along the image edge that has the ground color and the uppercolor over the ground color in the edge portion.
 10. The imageprocessing device according to claim 9, wherein the edge-portioncorrection area detector is configured to detect an edge-portioncorrection area in a colorless extension area which extends beyond anarea having the medium size in a borderless print image that is based onborderless print image data and has an image size larger than the mediumsize, the edge-portion correction area being adjacent to a colored areathat has the ground color and the upper color laid one over another inthe area having the medium size, and the correction processor isconfigured to correct the edge-portion correction area of the borderlessprint image.
 11. The image processing device according to claim 10,wherein the correction processor is configured to correct theedge-portion correction area of the borderless print image such that theedge-portion correction area has the ground color and the upper colorlaid one over another.
 12. The image processing device according toclaim 10, wherein the borderless print image data includes, for eachpixel, a ground-color pixel value representing density of the groundcolor and an upper-color pixel value representing density of the uppercolor, and the correction processor is configured to correct theedge-portion correction area such that the ground-color pixel value andthe upper-color pixel value of each pixel of the edge-portion correctionarea in the borderless print image are respectively replaced with thelargest value among the ground-color pixel values of pixels in a pixelsearch range including the pixel as a center pixel, and the largestvalue among the upper-color pixel values thereof.
 12. The imageprocessing device according to claim 10, wherein the borderless printimage data includes, for each pixel, a ground-color pixel valuerepresenting density of the ground color and an upper-color pixel valuerepresenting density of the upper color, and the correction processor isconfigured to correct the edge-portion correction area such that theground-color pixel value and the upper-color pixel value of each pixelof the edge-portion correction area in the borderless print image arerespectively replaced with the average values of the ground-color pixelvalues and the upper-color pixel values of pixels in a pixel searchrange including the pixel as a center pixel.
 13. The image processingdevice according to claim 10, wherein, when the borderless print imageis formed with a first image formation method, the edge-portioncorrection area detector detects the edge-portion correction area in theextension area of the borderless print image being based on theborderless print image data and having a first image size, and, when theborderless print image is formed with a second image formation method,the edge-portion correction area detector detects the edge-portioncorrection area in the extension area of the borderless print imagebeing based on the borderless print image data and having a second imagesize larger than the first image size.
 14. The image processing deviceaccording to claim 10, wherein the correction processor corrects theedge-portion correction area of the borderless print image of a firstimage size by using a first pixel search range of a size set accordingto an amount of first misregistration, and corrects the edge-portioncorrection area of the borderless print image of a second image size byusing a second pixel search range set according to an amount of secondmisregistration and larger than the first pixel search range.